diff --git a/requirements-dev.txt b/requirements-dev.txt
index f1db642..922b798 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -2,18 +2,15 @@
 --requirement requirements.txt
 
 # Postgresql database access
-psycopg2==2.9.2
+psycopg2==2.9.5
 
 # Documentation
-Sphinx==4.3.1
+Sphinx==6.0.0
 
 # Testing
-pytest==6.2.5
-pytest-cov==3.0.0
+pytest==7.2.0
+pytest-cov==4.0.0
 coveralls==3.3.1
 
 # Linting
-flake8==4.0.1
-mccabe==0.6.1
-pep8==1.7.1
-pyflakes==2.4.0
+flake8==6.0.0
diff --git a/requirements.txt b/requirements.txt
index 83ea0cc..599923d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,2 @@
-SQLAlchemy==1.4.28
-skosprovider==1.1.0
+SQLAlchemy==1.4.45
+skosprovider==1.2.0
\ No newline at end of file
diff --git a/setup.py b/setup.py
index c80754f..71236f3 100755
--- a/setup.py
+++ b/setup.py
@@ -1,8 +1,5 @@
 #!/usr/bin/env python
 
-import os
-import sys
-
 try:
     from setuptools import setup
 except ImportError:
@@ -13,7 +10,7 @@
 ]
 
 requires = [
-    'skosprovider>=1.1.0',
+    'skosprovider>=1.2.0',
     'sqlalchemy',
 ]
 
diff --git a/skosprovider_sqlalchemy/models.py b/skosprovider_sqlalchemy/models.py
index 3d6d14a..f83e81a 100644
--- a/skosprovider_sqlalchemy/models.py
+++ b/skosprovider_sqlalchemy/models.py
@@ -10,13 +10,13 @@
 from sqlalchemy import Text
 from sqlalchemy import UniqueConstraint
 from sqlalchemy import event
-from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy import orm
 from sqlalchemy.ext.hybrid import hybrid_property
 from sqlalchemy.orm import backref
 from sqlalchemy.orm import relationship
 
 log = logging.getLogger(__name__)
-Base = declarative_base()
+Base = orm.declarative_base()
 
 concept_label = Table(
     'concept_label',
@@ -199,7 +199,9 @@ class Thing(Base):
         single_parent=True
     )
 
-    conceptscheme = relationship('ConceptScheme', backref='concepts')
+    conceptscheme = relationship(
+        'ConceptScheme', backref=orm.backref('concepts', cascade_backrefs=False)
+    )
     conceptscheme_id = Column(
         Integer,
         ForeignKey('conceptscheme.id'),
@@ -253,19 +255,21 @@ class Concept(Thing):
     narrower_concepts = relationship(
         'Concept',
         secondary=concept_hierarchy_concept,
-        backref=backref('broader_concepts', collection_class=set),
+        backref=backref('broader_concepts', collection_class=set, cascade_backrefs=False),
         primaryjoin='Concept.id==concept_hierarchy_concept.c.concept_id_broader',
         secondaryjoin='Concept.id==concept_hierarchy_concept.c.concept_id_narrower',
-        collection_class=set
+        collection_class=set,
+        cascade_backrefs=False,
     )
 
     narrower_collections = relationship(
         'Collection',
         secondary=concept_hierarchy_collection,
-        backref=backref('broader_concepts', collection_class=set),
+        backref=backref('broader_concepts', collection_class=set, cascade_backrefs=False),
         primaryjoin='Concept.id==concept_hierarchy_collection.c.concept_id_broader',
         secondaryjoin='Concept.id==concept_hierarchy_collection.c.collection_id_narrower',
-        collection_class=set
+        collection_class=set,
+        cascade_backrefs=False,
     )
 
     __mapper_args__ = {
diff --git a/skosprovider_sqlalchemy/providers.py b/skosprovider_sqlalchemy/providers.py
index 3b5c381..c625281 100644
--- a/skosprovider_sqlalchemy/providers.py
+++ b/skosprovider_sqlalchemy/providers.py
@@ -8,8 +8,9 @@
 from skosprovider.skos import Note
 from skosprovider.skos import Source
 from skosprovider.uri import DefaultUrnGenerator
+from sqlalchemy import select
+from sqlalchemy.exc import NoResultFound
 from sqlalchemy.orm import joinedload
-from sqlalchemy.orm.exc import NoResultFound
 
 from skosprovider_sqlalchemy.models import Collection as CollectionModel
 from skosprovider_sqlalchemy.models import Concept as ConceptModel
@@ -56,7 +57,7 @@ def __init__(self, metadata, session, **kwargs):
         :param :class:`sqlachemy.orm.session.Session` session: The database
         session. This can also be a callable that returns a Session.
         '''
-        if not 'subject' in metadata:
+        if 'subject' not in metadata:
             metadata['subject'] = []
         self.metadata = metadata
         if 'uri_generator' in kwargs:
@@ -65,7 +66,7 @@ def __init__(self, metadata, session, **kwargs):
             self.uri_generator = DefaultUrnGenerator(self.metadata.get('id'))
         try:
             self.session = session()
-        except TypeError as e:
+        except TypeError:
             self.session = session
         try:
             self.conceptscheme_id = int(metadata.get(
@@ -94,28 +95,33 @@ def _get_concept_scheme(self):
         '''
         Find a :class:`skosprovider.skos.ConceptScheme` for this provider.
 
-        :param id: Id of a conceptscheme.
         :rtype: :class:`skosprovider.skos.ConceptScheme`
         '''
-        csm = self.session\
-                  .query(ConceptSchemeModel)\
-                  .options(joinedload('labels'))\
-                  .options(joinedload('notes'))\
-                  .options(joinedload('languages'))\
-                  .options(joinedload('sources'))\
-                  .get(self.conceptscheme_id)
+        csm = (
+            self.session
+            .get(
+                ConceptSchemeModel,
+                self.conceptscheme_id,
+                options=[
+                    joinedload(ConceptSchemeModel.labels),
+                    joinedload(ConceptSchemeModel.notes),
+                    joinedload(ConceptSchemeModel.languages),
+                    joinedload(ConceptSchemeModel.sources),
+                ]
+            )
+        )
         return ConceptScheme(
             uri=csm.uri,
             labels=[
-                Label(l.label, l.labeltype_id, l.language_id)
-                for l in csm.labels
+                Label(label.label, label.labeltype_id, label.language_id)
+                for label in csm.labels
             ],
             notes=[
                 Note(n.note, n.notetype_id, n.language_id, n.markup)
                 for n in csm.notes
             ],
             languages=[
-                l.id for l in csm.languages
+                language.id for language in csm.languages
             ],
             sources=[
                 Source(s.citation, s.markup) for s in csm.sources
@@ -130,40 +136,51 @@ def _from_thing(self, thing):
             to load.
         '''
         if thing.type and thing.type == 'collection':
+            if thing.uri is not None:
+                uri = thing.uri
+            else:
+                uri = self.uri_generator.generate(type='collection', id=thing.concept_id)
             return Collection(
                 id=thing.concept_id,
-                uri=thing.uri if thing.uri is not None else self.uri_generator.generate(type='collection', id=thing.concept_id),
+                uri=uri,
                 concept_scheme=self.concept_scheme,
                 labels=[
-                    Label(l.label, l.labeltype_id, l.language_id)
-                    for l in thing.labels
+                    Label(label.label, label.labeltype_id, label.language_id)
+                    for label in thing.labels
                 ],
                 notes=[
                     Note(n.note, n.notetype_id, n.language_id, n.markup)
                     for n in thing.notes
                 ],
                 sources=[
-                    Source(s.citation, s.markup ) for s in thing.sources
+                    Source(s.citation, s.markup) for s in thing.sources
                 ],
-                members=[member.concept_id for member in thing.members] if hasattr(thing, 'members') else [],
+                members=[member.concept_id for member in getattr(thing, 'members', [])],
                 member_of=[member_of.concept_id for member_of in thing.member_of],
-                superordinates=[broader_concept.concept_id for broader_concept in thing.broader_concepts],
+                superordinates=[
+                    broader_concept.concept_id
+                    for broader_concept in thing.broader_concepts
+                ],
                 infer_concept_relations=thing.infer_concept_relations
             )
         else:
+            if thing.uri is not None:
+                uri = thing.uri
+            else:
+                uri = self.uri_generator.generate(type='concept', id=thing.concept_id)
             matches = {}
             for m in thing.matches:
                 key = m.matchtype.name[:m.matchtype.name.find('Match')]
-                if not key in matches:
+                if key not in matches:
                     matches[key] = []
                 matches[key].append(m.uri)
             return Concept(
                 id=thing.concept_id,
-                uri=thing.uri if thing.uri is not None else self.uri_generator.generate(type='concept', id=thing.concept_id),
+                uri=uri,
                 concept_scheme=self.concept_scheme,
                 labels=[
-                    Label(l.label, l.labeltype_id, l.language_id)
-                    for l in thing.labels
+                    Label(label.label, label.labeltype_id, label.language_id)
+                    for label in thing.labels
                 ],
                 notes=[
                     Note(n.note, n.notetype_id, n.language_id, n.markup)
@@ -176,21 +193,25 @@ def _from_thing(self, thing):
                 narrower=[c.concept_id for c in thing.narrower_concepts],
                 related=[c.concept_id for c in thing.related_concepts],
                 member_of=[member_of.concept_id for member_of in thing.member_of],
-                subordinate_arrays=[narrower_collection.concept_id for narrower_collection in thing.narrower_collections],
+                subordinate_arrays=[
+                    narrower_collection.concept_id
+                    for narrower_collection in thing.narrower_collections
+                ],
                 matches=matches
             )
 
     def get_by_id(self, concept_id):
         try:
-            thing = self.session\
-                        .query(Thing)\
-                        .options(joinedload('labels'))\
-                        .options(joinedload('notes'))\
-                        .options(joinedload('sources'))\
-                        .filter(
-                            Thing.concept_id == str(concept_id),
-                            Thing.conceptscheme_id == self.conceptscheme_id
-                        ).one()
+            thing = self.session.execute(
+                select(Thing)
+                .options(joinedload(Thing.labels))
+                .options(joinedload(Thing.notes))
+                .options(joinedload(Thing.sources))
+                .filter(
+                    Thing.concept_id == str(concept_id),
+                    Thing.conceptscheme_id == self.conceptscheme_id
+                )
+            ).unique().scalar_one()
         except NoResultFound:
             return False
         return self._from_thing(thing)
@@ -209,15 +230,16 @@ def get_by_uri(self, uri):
             collection is unknown to the provider.
         '''
         try:
-            thing = self.session\
-                        .query(Thing)\
-                        .options(joinedload('labels'))\
-                        .options(joinedload('notes'))\
-                        .options(joinedload('sources'))\
-                        .filter(
-                            Thing.uri == uri,
-                            Thing.conceptscheme_id == self.conceptscheme_id
-                        ).one()
+            thing = self.session.execute(
+                select(Thing)
+                .options(joinedload(Thing.labels))
+                .options(joinedload(Thing.notes))
+                .options(joinedload(Thing.sources))
+                .filter(
+                    Thing.uri == uri,
+                    Thing.conceptscheme_id == self.conceptscheme_id
+                )
+            ).unique().scalar_one()
         except NoResultFound:
             return False
         return self._from_thing(thing)
@@ -227,12 +249,12 @@ def _get_id_and_label(self, c, lan):
         :param skosprovider_sqlalchemy.models.Thing c: A concept or collection.
         :param string lan: A language (eg. "en", "nl", "la", "fr")
         '''
-        l = c.label(lan)
+        label = c.label(lan)
         return {
             'id': c.concept_id,
             'uri': c.uri,
             'type': c.type,
-            'label': l.label if l is not None else None
+            'label': label.label if label is not None else None
         }
 
     def find(self, query, **kwargs):
@@ -245,11 +267,12 @@ def find(self, query, **kwargs):
                     'Please provide a URI to match with.'
                 )
             model = ConceptModel
-            q = self.session\
-                    .query(model)\
-                    .options(joinedload('labels'))\
-                    .join(MatchModel)\
-                    .filter(model.conceptscheme_id == self.conceptscheme_id)
+            q = (
+                select(model)
+                .options(joinedload(model.labels))
+                .join(MatchModel)
+                .filter(model.conceptscheme_id == self.conceptscheme_id)
+            )
             mtype = query['matches'].get('type')
             if mtype and mtype in Concept.matchtypes:
                 mtype += 'Match'
@@ -263,10 +286,11 @@ def find(self, query, **kwargs):
             else:
                 q = q.filter(MatchModel.uri == match_uri)
         else:
-            q = self.session\
-                    .query(model)\
-                    .options(joinedload('labels'))\
-                    .filter(model.conceptscheme_id == self.conceptscheme_id)
+            q = (
+                select(model)
+                .options(joinedload(model.labels))
+                .filter(model.conceptscheme_id == self.conceptscheme_id)
+            )
             if 'type' in query and query['type'] in ['concept', 'collection']:
                 q = q.filter(model.type == query['type'])
         if 'label' in query:
@@ -286,51 +310,67 @@ def find(self, query, **kwargs):
             else:
                 members = coll.members
             q = q.filter(model.concept_id.in_(members))
-        all = q.all()
+        things = self.session.execute(q).unique().scalars().all()
         sort = self._get_sort(**kwargs)
         sort_order = self._get_sort_order(**kwargs)
-        return [self._get_id_and_label(c, lan) for c in self._sort(all, sort, lan, sort_order=='desc')]
+        return [
+            self._get_id_and_label(c, lan)
+            for c in self._sort(things, sort, lan, sort_order == 'desc')
+        ]
 
     def get_all(self, **kwargs):
-        all = self.session\
-                  .query(Thing)\
-                  .options(joinedload('labels'))\
-                  .filter(Thing.conceptscheme_id == self.conceptscheme_id)\
-                  .all()
+        things = self.session.execute(
+            select(Thing)
+            .options(joinedload(Thing.labels))
+            .filter(Thing.conceptscheme_id == self.conceptscheme_id)
+        ).unique().scalars().all()
         lan = self._get_language(**kwargs)
         sort = self._get_sort(**kwargs)
         sort_order = self._get_sort_order(**kwargs)
-        return [self._get_id_and_label(c, lan) for c in self._sort(all, sort, lan, sort_order=='desc')]
+        return [
+            self._get_id_and_label(c, lan)
+            for c in self._sort(things, sort, lan, sort_order == 'desc')
+        ]
 
     def get_top_concepts(self, **kwargs):
         # get the concepts that have no direct broader concept
-        top = self.session\
-                  .query(ConceptModel)\
-                  .options(joinedload('labels'))\
-                  .filter(
-                    ConceptModel.conceptscheme_id == self.conceptscheme_id,
-                    ConceptModel.broader_concepts == None
-                  ).all()
+        top = self.session.execute(
+            select(ConceptModel)
+            .options(joinedload(ConceptModel.labels))
+            .filter(
+                ConceptModel.conceptscheme_id == self.conceptscheme_id,
+                ~ConceptModel.broader_concepts.any()
+            )
+        ).unique().scalars().all()
+
         # check if they have an indirect broader concept
         def _has_higher_concept(c):
             for coll in c.member_of:
-                if coll.infer_concept_relations and (coll.broader_concepts or _has_higher_concept(coll)):
+                if (
+                    coll.infer_concept_relations
+                    and coll.broader_concepts or _has_higher_concept(coll)
+                ):
                     return True
             return False
         top = [c for c in top if not _has_higher_concept(c)]
         lan = self._get_language(**kwargs)
         sort = self._get_sort(**kwargs)
         sort_order = self._get_sort_order(**kwargs)
-        return [self._get_id_and_label(c, lan) for c in self._sort(top, sort, lan, sort_order=='desc')]
 
-    def expand(self, id):
+        return [
+            self._get_id_and_label(c, lan)
+            for c in self._sort(top, sort, lan, sort_order == 'desc')
+        ]
+
+    def expand(self, concept_id):
         try:
-            thing = self.session\
-                        .query(Thing)\
-                        .filter(
-                            Thing.concept_id == str(id),
-                            Thing.conceptscheme_id == self.conceptscheme_id
-                        ).one()
+            thing = self.session.execute(
+                select(Thing)
+                .filter(
+                    Thing.concept_id == str(concept_id),
+                    Thing.conceptscheme_id == self.conceptscheme_id
+                )
+            ).scalar_one()
         except NoResultFound:
             return False
 
@@ -355,27 +395,30 @@ def _expand_recurse(self, thing):
 
     def _expand_visit(self, thing):
         if thing.type == 'collection':
-            ret = []
+            concept_ids = []
             for m in thing.members:
-                ret += self._expand_visit(m)
+                concept_ids += self._expand_visit(m)
         else:
             try:
-                cov = self.session\
-                          .query(Visitation.lft, Visitation.rght)\
-                          .filter(Visitation.conceptscheme_id == self.conceptscheme_id)\
-                          .filter(Visitation.concept_id == thing.id)\
-                          .one()
+                visitation = self.session.execute(
+                    select(Visitation.lft, Visitation.rght)
+                    .filter(
+                        Visitation.conceptscheme_id == self.conceptscheme_id,
+                        Visitation.concept_id == thing.id
+                    )
+                ).one()
             except NoResultFound:
                 return self._expand_recurse(thing)
 
-            ids = self.session\
-                      .query(Thing.concept_id)\
-                      .join(Visitation)\
-                      .filter(Thing.conceptscheme_id == self.conceptscheme_id)\
-                      .filter(Visitation.lft.between(cov[0], cov[1]))\
-                      .all()
-            ret = [id[0] for id in ids]
-        return list(set(ret))
+            concept_ids = self.session.execute(
+                select(Thing.concept_id)
+                .join(Visitation)
+                .filter(
+                    Thing.conceptscheme_id == self.conceptscheme_id,
+                    Visitation.lft.between(visitation.lft, visitation.rght)
+                )
+            ).scalars().all()
+        return list(set(concept_ids))
 
     def get_top_display(self, **kwargs):
         '''
@@ -390,34 +433,39 @@ def get_top_display(self, **kwargs):
             the `**kwargs` parameter, the default language of the provider
             and falls back to `en` if nothing is present.
         '''
-        tco = self.session\
-                  .query(ConceptModel)\
-                  .options(joinedload('labels'))\
-                  .filter(
-                    ConceptModel.conceptscheme_id == self.conceptscheme_id,
-                    ConceptModel.broader_concepts == None,
-                    ConceptModel.member_of == None
-                  ).all()
-        tcl = self.session\
-                  .query(CollectionModel)\
-                  .options(joinedload('labels'))\
-                  .filter(
-                    CollectionModel.conceptscheme_id == self.conceptscheme_id,
-                    CollectionModel.broader_concepts == None,
-                    CollectionModel.member_of == None
-                  ).all()
-        res = tco + tcl
+        top_concepts = self.session.execute(
+            select(ConceptModel)
+            .options(joinedload(ConceptModel.labels))
+            .filter(
+                ConceptModel.conceptscheme_id == self.conceptscheme_id,
+                ~ConceptModel.broader_concepts.any(),
+                ~ConceptModel.member_of.any()
+            )
+        ).unique().scalars().all()
+        top_collections = self.session.execute(
+            select(CollectionModel)
+            .options(joinedload(CollectionModel.labels))
+            .filter(
+                CollectionModel.conceptscheme_id == self.conceptscheme_id,
+                ~CollectionModel.broader_concepts.any(),
+                ~CollectionModel.member_of.any()
+            )
+        ).unique().scalars().all()
+        res = top_concepts + top_collections
         lan = self._get_language(**kwargs)
         sort = self._get_sort(**kwargs)
         sort_order = self._get_sort_order(**kwargs)
-        return [self._get_id_and_label(c, lan) for c in self._sort(res, sort, lan, sort_order=='desc')]
+        return [
+            self._get_id_and_label(c, lan)
+            for c in self._sort(res, sort, lan, sort_order == 'desc')
+        ]
 
-    def get_children_display(self, id, **kwargs):
+    def get_children_display(self, thing_id, **kwargs):
         '''
         Return a list of concepts or collections that should be displayed
         under this concept or collection.
 
-        :param id: A concept or collection id.
+        :param thing_id: A concept or collection id.
         :rtype: A list of concepts and collections. For each an
             id is present and a label. The label is determined by looking at
             the `**kwargs` parameter, the default language of the provider
@@ -425,12 +473,13 @@ def get_children_display(self, id, **kwargs):
             exist, return `False`.
         '''
         try:
-            thing = self.session\
-                        .query(Thing)\
-                        .filter(
-                            Thing.concept_id == str(id),
-                            Thing.conceptscheme_id == self.conceptscheme_id
-                        ).one()
+            thing = self.session.execute(
+                select(Thing)
+                .filter(
+                    Thing.concept_id == str(thing_id),
+                    Thing.conceptscheme_id == self.conceptscheme_id
+                )
+            ).scalar_one()
         except NoResultFound:
             return False
         lan = self._get_language(**kwargs)
@@ -438,10 +487,13 @@ def get_children_display(self, id, **kwargs):
         if thing.type == 'concept':
             if len(thing.narrower_collections) > 0:
                 res += thing.narrower_collections
-            elif len(thing.narrower_concepts)>0:
+            elif len(thing.narrower_concepts) > 0:
                 res += thing.narrower_concepts
         if thing.type == 'collection' and hasattr(thing, 'members'):
             res += thing.members
         sort = self._get_sort(**kwargs)
         sort_order = self._get_sort_order(**kwargs)
-        return [self._get_id_and_label(c, lan) for c in self._sort(res, sort, lan, sort_order=='desc')]
+        return [
+            self._get_id_and_label(c, lan)
+            for c in self._sort(res, sort, lan, sort_order == 'desc')
+        ]
diff --git a/skosprovider_sqlalchemy/scripts/calc_visitation.py b/skosprovider_sqlalchemy/scripts/calc_visitation.py
index 0c7cc43..6ac0343 100644
--- a/skosprovider_sqlalchemy/scripts/calc_visitation.py
+++ b/skosprovider_sqlalchemy/scripts/calc_visitation.py
@@ -27,7 +27,7 @@ def main(argv=sys.argv):
         bind=engine,
     )()
     vc = VisitationCalculator(session)
-    cs = session.query(ConceptScheme).get(scheme_id)
+    cs = session.get(ConceptScheme, scheme_id)
     visit = vc.visit(cs)
     for v in visit:
         vrow = Visitation(
diff --git a/skosprovider_sqlalchemy/utils.py b/skosprovider_sqlalchemy/utils.py
index 62caae0..6e7f5fe 100644
--- a/skosprovider_sqlalchemy/utils.py
+++ b/skosprovider_sqlalchemy/utils.py
@@ -3,7 +3,8 @@
 from language_tags import tags
 from skosprovider.skos import Collection
 from skosprovider.skos import Concept
-from sqlalchemy.orm.exc import NoResultFound
+from sqlalchemy import select
+from sqlalchemy.exc import NoResultFound
 
 from skosprovider_sqlalchemy.models import Collection as CollectionModel
 from skosprovider_sqlalchemy.models import Concept as ConceptModel
@@ -56,6 +57,7 @@ def import_provider(provider, conceptscheme, session):
                 uri=c.uri,
                 conceptscheme=conceptscheme
             )
+        session.add(cm)
         _add_labels(cm, c.labels, session)
         _add_notes(cm, c.notes, session)
         _add_sources(cm, c.sources, session)
@@ -65,7 +67,6 @@ def import_provider(provider, conceptscheme, session):
                 for m in c.matches[mt]:
                     match = MatchModel(matchtype_id=matchtype, uri=m)
                     cm.matches.append(match)
-        session.add(cm)
 
     session.flush()
 
@@ -73,17 +74,23 @@ def import_provider(provider, conceptscheme, session):
     for stuff in provider.get_all():
         c = provider.get_by_id(stuff['id'])
         if isinstance(c, Concept):
-            cm = session.query(ConceptModel) \
-                .filter(ConceptModel.conceptscheme_id == conceptscheme.id) \
-                .filter(ConceptModel.concept_id == str(c.id)) \
-                .one()
+            cm = session.execute(
+                select(ConceptModel)
+                .filter(
+                    ConceptModel.conceptscheme_id == conceptscheme.id,
+                    ConceptModel.concept_id == str(c.id)
+                )
+            ).scalar_one()
             if len(c.narrower) > 0:
                 for nc in c.narrower:
                     try:
-                        nc = session.query(ConceptModel) \
-                            .filter(ConceptModel.conceptscheme_id == conceptscheme.id) \
-                            .filter(ConceptModel.concept_id == str(nc)) \
-                            .one()
+                        nc = session.execute(
+                            select(ConceptModel)
+                            .filter(
+                                ConceptModel.conceptscheme_id == conceptscheme.id,
+                                ConceptModel.concept_id == str(nc)
+                            )
+                        ).scalar_one()
                         cm.narrower_concepts.add(nc)
                     except NoResultFound:
                         log.warning(
@@ -92,10 +99,13 @@ def import_provider(provider, conceptscheme, session):
             if len(c.subordinate_arrays) > 0:
                 for sa in c.subordinate_arrays:
                     try:
-                        sa = session.query(CollectionModel) \
-                            .filter(CollectionModel.conceptscheme_id == conceptscheme.id) \
-                            .filter(CollectionModel.concept_id == str(sa)) \
-                            .one()
+                        sa = session.execute(
+                            select(CollectionModel)
+                            .filter(
+                                CollectionModel.conceptscheme_id == conceptscheme.id,
+                                CollectionModel.concept_id == str(sa)
+                            )
+                        ).scalar_one()
                         cm.narrower_collections.add(sa)
                     except NoResultFound:
                         log.warning(
@@ -104,26 +114,35 @@ def import_provider(provider, conceptscheme, session):
             if len(c.related) > 0:
                 for rc in c.related:
                     try:
-                        rc = session.query(ConceptModel) \
-                            .filter(ConceptModel.conceptscheme_id == conceptscheme.id) \
-                            .filter(ConceptModel.concept_id == str(rc)) \
-                            .one()
+                        rc = session.execute(
+                            select(ConceptModel)
+                            .filter(
+                                ConceptModel.conceptscheme_id == conceptscheme.id,
+                                ConceptModel.concept_id == str(rc)
+                            )
+                        ).scalar_one()
                         cm.related_concepts.add(rc)
                     except NoResultFound:
                         log.warning(
                             'Tried to add a relation %s related %s, but target \
                             does not exist. Relation will be lost.' % (c.id, rc))
         elif isinstance(c, Collection) and len(c.members) > 0:
-            cm = session.query(CollectionModel) \
-                .filter(ConceptModel.conceptscheme_id == conceptscheme.id) \
-                .filter(ConceptModel.concept_id == str(c.id)) \
-                .one()
+            cm = session.execute(
+                select(CollectionModel)
+                .filter(
+                    ConceptModel.conceptscheme_id == conceptscheme.id,
+                    ConceptModel.concept_id == str(c.id)
+                )
+            ).scalar_one()
             for mc in c.members:
                 try:
-                    mc = session.query(ThingModel) \
-                        .filter(ConceptModel.conceptscheme_id == conceptscheme.id) \
-                        .filter(ConceptModel.concept_id == str(mc)) \
-                        .one()
+                    mc = session.execute(
+                        select(ThingModel)
+                        .filter(
+                            ConceptModel.conceptscheme_id == conceptscheme.id,
+                            ConceptModel.concept_id == str(mc)
+                        )
+                    ).scalar_one()
                     cm.members.add(mc)
                 except NoResultFound:
                     log.warning(
@@ -139,9 +158,9 @@ def _check_language(language_tag, session):
     :param session: Database session to use
     :rtype: :class:`skosprovider_sqlalchemy.models.Language`
     '''
-    if not language_tag: # pragma: no cover
+    if not language_tag:  # pragma: no cover
         language_tag = 'und'
-    l = session.query(LanguageModel).get(language_tag)
+    l = session.get(LanguageModel, language_tag)
     if not l:
         if not tags.check(language_tag):
             raise ValueError('Unable to import provider. Invalid language tag: %s' % language_tag)
@@ -200,6 +219,7 @@ def _add_sources(target, sources, session):
         ))
     return target
 
+
 class VisitationCalculator:
     '''
     Generates a nested set for a conceptscheme.
@@ -211,6 +231,9 @@ def __init__(self, session):
             session.
         '''
         self.session = session
+        self.count = 0
+        self.depth = 0
+        self.visitation = []
 
     def visit(self, conceptscheme):
         '''
@@ -225,15 +248,21 @@ def visit(self, conceptscheme):
         self.depth = 0
         self.visitation = []
         # get all possible top concepts
-        topc = self.session \
-            .query(ConceptModel) \
-            .filter(ConceptModel.conceptscheme == conceptscheme) \
-            .filter(ConceptModel.broader_concepts == None) \
-            .all()
+        topc = self.session.execute(
+            select(ConceptModel)
+            .filter(
+                ConceptModel.conceptscheme == conceptscheme,
+                ~ConceptModel.broader_concepts.any()
+            )
+        ).scalars().all()
+
         # check if they have an indirect broader concept
         def _has_higher_concept(c):
             for coll in c.member_of:
-                if coll.infer_concept_relations and (coll.broader_concepts or _has_higher_concept(coll)):
+                if (
+                    coll.infer_concept_relations
+                    and coll.broader_concepts or _has_higher_concept(coll)
+                ):
                     return True
             return False
         topc = [c for c in topc if not _has_higher_concept(c)]
diff --git a/tests/conftest.py b/tests/conftest.py
index 308d6e0..fa0a18f 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,4 +1,5 @@
 import pytest
+from sqlalchemy import select
 from sqlalchemy.orm import sessionmaker
 from sqlalchemy import create_engine
 
@@ -16,7 +17,7 @@ def pytest_addoption(parser):
 def engine(request):
     engine = create_engine(
         request.config.getoption('--sqlalchemy_url'),
-        echo=True
+        echo=True,
     )
 
     return engine
@@ -41,8 +42,8 @@ def create_data(session):
         Match,
         Language
     )
-    en = session.query(Language).get('en')
-    nl = session.query(Language).get('nl')
+    en = session.get(Language, 'en')
+    nl = session.get(Language, 'nl')
     cs = ConceptScheme(
         id=1,
         uri='urn:x-skosprovider:test',
@@ -177,7 +178,7 @@ def create_visitation(session):
         ConceptScheme
     )
     vc = VisitationCalculator(session)
-    conceptschemes = session.query(ConceptScheme).all()
+    conceptschemes = session.execute(select(ConceptScheme)).scalars().all()
     for cs in conceptschemes:
         visit = vc.visit(cs)
         for v in visit:
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 52568f6..c840382 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -1,6 +1,7 @@
 import csv
 import os
 
+from sqlalchemy import select
 from sqlalchemy.orm import session
 
 from skosprovider_sqlalchemy.models import Base
@@ -231,9 +232,8 @@ def _get_materials():
 def _get_heritage_types():
     import json
 
-    typology_data = json.load(
-        open(os.path.join(os.path.dirname(__file__), 'data', 'typologie.js')),
-    )['typologie']
+    with open(os.path.join(os.path.dirname(__file__), 'data', 'typologie.js')) as f:
+        typology_data = json.load(f)['typologie']
     from skosprovider.providers import DictionaryProvider
     from skosprovider.uri import UriPatternGenerator
     from skosprovider.skos import ConceptScheme
@@ -268,9 +268,8 @@ def _get_heritage_types():
 def _get_event_types():
     import json
 
-    event_data = json.load(
-        open(os.path.join(os.path.dirname(__file__), 'data', 'gebeurtenis.js')),
-    )['gebeurtenis']
+    with open(os.path.join(os.path.dirname(__file__), 'data', 'gebeurtenis.js')) as f:
+        event_data = json.load(f)['gebeurtenis']
     from skosprovider.providers import DictionaryProvider
     from skosprovider.uri import UriPatternGenerator
 
@@ -314,7 +313,7 @@ def test_empty_provider(self):
         cs = self._get_cs()
         self.session.add(cs)
         import_provider(p, cs, self.session)
-        scheme = self.session.query(ConceptSchemeModel).get(68)
+        scheme = self.session.get(ConceptSchemeModel, 68)
         assert scheme == cs
 
     def test_menu(self):
@@ -326,10 +325,13 @@ def test_menu(self):
         cs = self._get_cs()
         self.session.add(cs)
         import_provider(csvprovider, cs, self.session)
-        lobster = self.session.query(ConceptModel) \
-            .filter(ConceptModel.conceptscheme == cs) \
-            .filter(ConceptModel.concept_id == '11') \
-            .one()
+        lobster = self.session.execute(
+            select(ConceptModel) 
+            .filter(
+                ConceptModel.conceptscheme == cs, 
+                ConceptModel.concept_id == '11'
+            )
+        ).scalar_one()
         assert 11 == lobster.concept_id
         assert 'urn:x-skosprovider:menu:11' == lobster.uri
         assert 'Lobster Thermidor' == str(lobster.label())
@@ -345,30 +347,39 @@ def test_geo(self):
         cs = self._get_cs()
         self.session.add(cs)
         import_provider(geoprovider, cs, self.session)
-        world = self.session.query(ConceptModel) \
-            .filter(ConceptModel.conceptscheme == cs) \
-            .filter(ConceptModel.concept_id == '1') \
-            .one()
+        world = self.session.execute(
+            select(ConceptModel)
+            .filter(
+                ConceptModel.conceptscheme == cs,
+                ConceptModel.concept_id == '1'
+            )
+        ).scalar_one()
         assert world.concept_id == 1
         assert 'urn:x-skosprovider:geography:1' == world.uri
         assert 'World' == str(world.label('en'))
         assert 1 == len(world.labels)
         assert 2 == len(world.narrower_concepts)
 
-        dutch = self.session.query(CollectionModel) \
-            .filter(CollectionModel.conceptscheme == cs) \
-            .filter(CollectionModel.concept_id == '333') \
-            .one()
+        dutch = self.session.execute(
+            select(CollectionModel)
+            .filter(
+                CollectionModel.conceptscheme == cs,
+                CollectionModel.concept_id == '333'
+            )
+        ).scalar_one()
         assert 333 == dutch.concept_id
         assert 'urn:x-skosprovider:geography:333' == dutch.uri
         assert 'collection' == dutch.type
         assert 1 == len(dutch.labels)
         assert 4 == len(dutch.members)
 
-        netherlands = self.session.query(ConceptModel) \
-            .filter(ConceptModel.conceptscheme == cs) \
-            .filter(ConceptModel.concept_id == '10') \
-            .one()
+        netherlands = self.session.execute(
+            select(ConceptModel)
+            .filter(
+                ConceptModel.conceptscheme == cs, 
+                ConceptModel.concept_id == '10',
+            )
+        ).scalar_one()
         assert 10 == netherlands.concept_id
         assert 'concept' == netherlands.type
         assert 1 == len(netherlands.labels)
@@ -384,15 +395,21 @@ def test_buildings(self):
         cs = self._get_cs()
         self.session.add(cs)
         import_provider(buildingprovider, cs, self.session)
-        castle = self.session.query(ConceptModel) \
-            .filter(ConceptModel.conceptscheme == cs) \
-            .filter(ConceptModel.concept_id == '2') \
-            .one()
+        castle = self.session.execute(
+            select(ConceptModel)
+            .filter(
+                ConceptModel.conceptscheme == cs,
+                ConceptModel.concept_id == '2'
+            )
+        ).scalar_one()
         assert 2 == len(castle.broader_concepts)
-        hut = self.session.query(ConceptModel) \
-            .filter(ConceptModel.conceptscheme == cs) \
-            .filter(ConceptModel.concept_id == '4') \
-            .one()
+        hut = self.session.execute(
+            select(ConceptModel)
+            .filter(
+                ConceptModel.conceptscheme == cs, 
+                ConceptModel.concept_id == '4'
+            )
+        ).scalar_one()
         assert 1 == len(hut.broader_concepts)
         assert 1 == len(hut.matches)
         assert 'exactMatch' == hut.matches[0].matchtype_id
@@ -407,10 +424,13 @@ def test_heritage_types(self):
         cs = self._get_cs()
         self.session.add(cs)
         import_provider(heritagetypesprovider, cs, self.session)
-        bomen = self.session.query(ConceptModel) \
-            .filter(ConceptModel.conceptscheme == cs) \
-            .filter(ConceptModel.concept_id == '72') \
-            .one()
+        bomen = self.session.execute(
+            select(ConceptModel)
+            .filter(
+                ConceptModel.conceptscheme == cs, 
+                ConceptModel.concept_id == '72'
+            )
+        ).scalar_one()
         assert 2 == len(bomen.narrower_collections)
         assert 2 == len(cs.labels)
         assert 'Erfgoedtypes' == cs.label('nl').label
@@ -426,10 +446,13 @@ def test_event_types(self):
         cs = self._get_cs()
         self.session.add(cs)
         import_provider(eventtypesprovider, cs, self.session)
-        archeologische_opgravingen = self.session.query(ConceptModel) \
-            .filter(ConceptModel.conceptscheme == cs) \
-            .filter(ConceptModel.concept_id == '38') \
-            .one()
+        archeologische_opgravingen = self.session.execute(
+            select(ConceptModel)
+            .filter(
+                ConceptModel.conceptscheme == cs,
+                ConceptModel.concept_id == '38'
+            )
+        ).scalar_one()
         assert 3 == len(archeologische_opgravingen.narrower_collections)
 
     def test_materials(self):
@@ -441,9 +464,10 @@ def test_materials(self):
         cs = self._get_cs()
         self.session.add(cs)
         import_provider(materialsprovider, cs, self.session)
-        materials = self.session.query(ThingModel) \
-            .filter(ThingModel.conceptscheme == cs) \
-            .all()
+        materials = self.session.execute(
+            select(ThingModel)
+            .filter(ThingModel.conceptscheme == cs)
+        ).scalars().all()
         assert 2 == len(materials)
 
 
@@ -538,7 +562,7 @@ def test_geo(self):
         visit = vc.visit(cs)
         assert 10 == len(visit)
         world = visit[0]
-        assert self.session.query(ConceptModel).get(world['id']).concept_id == 1
+        assert self.session.get(ConceptModel, world['id']).concept_id == 1
         assert 1 == world['lft']
         assert 20 == world['rght']
         assert 1 == world['depth']
@@ -563,7 +587,7 @@ def test_buildings(self):
         visit = vc.visit(cs)
         assert len(visit) == 5
         # Check that castle is present twice
-        ids = [self.session.query(ConceptModel).get(v['id']).concept_id for v in visit]
+        ids = [self.session.get(ConceptModel, v['id']).concept_id for v in visit]
         assert ids.count(2) == 2
         for v in visit:
             # Check that fortification has one child