feat: make PageLayout.elements a cached property (#414)

- default `PageLayout.get_elements_with_detection_model` now returns
`LayoutElements`
- `PageLayout.elements` is a cached property computed from
`elements_array` property to save memory and cpu costs

CHANGELOG.md

@@ -1,6 +1,7 @@
-## 0.8.8-dev0
+## 0.8.8-dev1
 
 * fix: pdfminer-six dependencies
+* feat: `PageLayout.elements` is now a `cached_property` to reduce unecessary memory and cpu costs
 
 ## 0.8.7
 

test_unstructured_inference/inference/test_layout.py

@@ -116,7 +116,7 @@ def test_get_page_elements(monkeypatch, mock_final_layout):
     )
     elements = page.get_elements_with_detection_model(inplace=False)
     page.get_elements_with_detection_model(inplace=True)
-    assert elements == page.elements
+    assert elements == page.elements_array
 
 
 class MockPool:

unstructured_inference/__version__.py

@@ -1 +1 @@
-__version__ = "0.8.8-dev0"  # pragma: no cover
+__version__ = "0.8.8-dev1"  # pragma: no cover

unstructured_inference/inference/layout.py

@@ -2,6 +2,7 @@
 
 import os
 import tempfile
+from functools import cached_property
 from pathlib import PurePath
 from typing import Any, BinaryIO, Collection, List, Optional, Union, cast
 
@@ -149,7 +150,6 @@ def __init__(
         self.number = number
         self.detection_model = detection_model
         self.element_extraction_model = element_extraction_model
-        self.elements: Collection[LayoutElement] = []
         self.elements_array: LayoutElements | None = None
         self.password = password
         # NOTE(alan): Dropped LocationlessLayoutElement that was created for chipper - chipper has
@@ -159,10 +159,18 @@ def __init__(
     def __str__(self) -> str:
         return "\n\n".join([str(element) for element in self.elements])
 
+    @cached_property
+    def elements(self) -> Collection[LayoutElement]:
+        """return a list of layout elements from the array data structure; intended for backward
+        compatibility"""
+        if self.elements_array is None:
+            return []
+        return self.elements_array.as_list()
+
     def get_elements_using_image_extraction(
         self,
         inplace=True,
-    ) -> Optional[List[LayoutElement]]:
+    ) -> Optional[list[LayoutElement]]:
         """Uses end-to-end text element extraction model to extract the elements on the page."""
         if self.element_extraction_model is None:
             raise ValueError(
@@ -178,8 +186,7 @@ def get_elements_using_image_extraction(
     def get_elements_with_detection_model(
         self,
         inplace: bool = True,
-        array_only: bool = False,
-    ) -> Optional[List[LayoutElement]]:
+    ) -> Optional[LayoutElements]:
         """Uses specified model to detect the elements on the page."""
         if self.detection_model is None:
             model = get_model()
@@ -198,11 +205,9 @@ def get_elements_with_detection_model(
 
         if inplace:
             self.elements_array = inferred_layout
-            if not array_only:
-                self.elements = inferred_layout.as_list()
             return None
 
-        return inferred_layout.as_list()
+        return inferred_layout
 
     def _get_image_array(self) -> Union[np.ndarray[Any, Any], None]:
         """Converts the raw image into a numpy array."""