Undo adding is_empty to Parent and add it to FiniteWords

src/sage/combinat/words/words.py

@@ -350,6 +350,19 @@ def __init__(self, alphabet=None, category=None):
             category = category.Finite()
         super().__init__(alphabet, category)
 
+    def is_empty(self):
+        """
+        Return False, because the empty word is in the set.
+
+        TESTS::
+
+            sage: FiniteWords('ab').is_empty()
+            False
+            sage: FiniteWords([]).is_empty()
+            False
+        """
+        return False
+
     def cardinality(self):
         r"""
         Return the cardinality of this set.

src/sage/structure/parent.pyx

@@ -1235,13 +1235,6 @@ cdef class Parent(sage.structure.category_object.CategoryObject):
         """
         return True
 
-    def is_empty(self):
-        """
-        Default implementation of the method :meth:`is_empty`.
-        Delegates to :meth:`__bool__`.
-        """
-        return not bool(self)
-
     # Should be moved and merged into the EnumeratedSets() category (#12955)
     def __getitem__(self, n):
         """