unstructured, community, initialize langchain-unstructured package (#22779)

#### Update (2): 
A single `UnstructuredLoader` is added to handle both local and api
partitioning. This loader also handles single or multiple documents.

#### Changes in `community`:
Changes here do not affect users. In the initial process of using the
SDK for the API Loaders, the Loaders in community were refactored.
Other changes include:
The `UnstructuredBaseLoader` has a new check to see if both
`mode="paged"` and `chunking_strategy="by_page"`. It also now has
`Element.element_id` added to the `Document.metadata`.
`UnstructuredAPIFileLoader` and `UnstructuredAPIFileIOLoader`. As such,
now both directly inherit from `UnstructuredBaseLoader` and initialize
their `file_path`/`file` attributes respectively and implement their own
`_post_process_elements` methods.

--------
#### Update:
New SDK Loaders in a [partner
package](https://python.langchain.com/v0.1/docs/contributing/integrations/#partner-package-in-langchain-repo)
are introduced to prevent breaking changes for users (see discussion
below).

##### TODO:
- [x] Test docstring examples
--------
- **Description:** UnstructuredAPIFileIOLoader and
UnstructuredAPIFileLoader calls to the unstructured api are now made
using the unstructured-client sdk.
- **New Dependencies:** unstructured-client

- [x] **Add tests and docs**: If you're adding a new integration, please
include
- [x] a test for the integration, preferably unit tests that do not rely
on network access,
- [x] update the description in
`docs/docs/integrations/providers/unstructured.mdx`
- [x] **Lint and test**: Run `make format`, `make lint` and `make test`
from the root of the package(s) you've modified. See contribution
guidelines for more: https://python.langchain.com/docs/contributing/

Additional guidelines:
- Make sure optional dependencies are imported within a function.
- Please do not add dependencies to pyproject.toml files (even optional
ones) unless they are required for unit tests.
- Most PRs should not touch more than one package.
- Changes should be backwards compatible.
- If you are adding something to community, do not re-import it in
langchain.

TODO:
- [x] Update
https://python.langchain.com/v0.1/docs/integrations/document_loaders/unstructured_file/#unstructured-api
-
`langchain/docs/docs/integrations/document_loaders/unstructured_file.ipynb`
- The description here needs to indicate that users should install
`unstructured-client` instead of `unstructured`. Read over closely to
look for any other changes that need to be made.
- [x] Update the `lazy_load` method in `UnstructuredBaseLoader` to
handle json responses from the API instead of just lists of elements.
- This method may need to be overwritten by the API loaders instead of
changing it in the `UnstructuredBaseLoader`.
- [x] Update the documentation links in the class docstrings (the
Unstructured documents have moved)
- [x] Update Document.metadata to include `element_id` (see thread
[here](https://unstructuredw-kbe4326.slack.com/archives/C044N0YV08G/p1718187499818419))

---------

Signed-off-by: ChengZi <chen.zhang@zilliz.com>
Co-authored-by: Erick Friis <erick@langchain.dev>
Co-authored-by: Isaac Francisco <78627776+isahers1@users.noreply.github.com>
Co-authored-by: ChengZi <chen.zhang@zilliz.com>

libs/partners/unstructured/tests/unit_tests/test_document_loaders.py

@@ -0,0 +1,178 @@
+from pathlib import Path
+from typing import Any, Callable
+from unittest import mock
+from unittest.mock import Mock, mock_open, patch
+
+import pytest
+from unstructured.documents.elements import Text  # type: ignore
+
+from langchain_unstructured.document_loaders import (
+    _SingleDocumentLoader,  # type: ignore
+)
+
+EXAMPLE_DOCS_DIRECTORY = str(
+    Path(__file__).parent.parent.parent.parent.parent
+    / "community/tests/integration_tests/examples/"
+)
+
+
+# --- _SingleDocumentLoader._get_content() ---
+
+
+def test_it_gets_content_from_file() -> None:
+    mock_file = Mock()
+    mock_file.read.return_value = b"content from file"
+    loader = _SingleDocumentLoader(
+        client=Mock(), file=mock_file, metadata_filename="fake.txt"
+    )
+
+    content = loader._file_content  # type: ignore
+
+    assert content == b"content from file"
+    mock_file.read.assert_called_once()
+
+
+@patch("builtins.open", new_callable=mock_open, read_data=b"content from file_path")
+def test_it_gets_content_from_file_path(mock_file: Mock) -> None:
+    loader = _SingleDocumentLoader(client=Mock(), file_path="dummy_path")
+
+    content = loader._file_content  # type: ignore
+
+    assert content == b"content from file_path"
+    mock_file.assert_called_once_with("dummy_path", "rb")
+    handle = mock_file()
+    handle.read.assert_called_once()
+
+
+def test_it_raises_value_error_without_file_or_file_path() -> None:
+    loader = _SingleDocumentLoader(
+        client=Mock(),
+    )
+
+    with pytest.raises(ValueError) as e:
+        loader._file_content  # type: ignore
+
+    assert str(e.value) == "file or file_path must be defined."
+
+
+# --- _SingleDocumentLoader._elements_json ---
+
+
+def test_it_calls_elements_via_api_with_valid_args() -> None:
+    with patch.object(
+        _SingleDocumentLoader, "_elements_via_api", new_callable=mock.PropertyMock
+    ) as mock_elements_via_api:
+        mock_elements_via_api.return_value = [{"element": "data"}]
+        loader = _SingleDocumentLoader(
+            client=Mock(),
+            # Minimum required args for self._elements_via_api to be called:
+            partition_via_api=True,
+            api_key="some_key",
+        )
+
+        result = loader._elements_json  # type: ignore
+
+    mock_elements_via_api.assert_called_once()
+    assert result == [{"element": "data"}]
+
+
+@patch.object(_SingleDocumentLoader, "_convert_elements_to_dicts")
+def test_it_partitions_locally_by_default(mock_convert_elements_to_dicts: Mock) -> None:
+    mock_convert_elements_to_dicts.return_value = [{}]
+    with patch.object(
+        _SingleDocumentLoader, "_elements_via_local", new_callable=mock.PropertyMock
+    ) as mock_elements_via_local:
+        mock_elements_via_local.return_value = [{}]
+        # Minimum required args for self._elements_via_api to be called:
+        loader = _SingleDocumentLoader(
+            client=Mock(),
+        )
+
+        result = loader._elements_json  # type: ignore
+
+    mock_elements_via_local.assert_called_once_with()
+    mock_convert_elements_to_dicts.assert_called_once_with([{}])
+    assert result == [{}]
+
+
+def test_it_partitions_locally_and_logs_warning_with_partition_via_api_False(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    with patch.object(
+        _SingleDocumentLoader, "_elements_via_local"
+    ) as mock_get_elements_locally:
+        mock_get_elements_locally.return_value = [Text("Mock text element.")]
+        loader = _SingleDocumentLoader(
+            client=Mock(), partition_via_api=False, api_key="some_key"
+        )
+
+        _ = loader._elements_json  # type: ignore
+
+
+# -- fixtures -------------------------------
+
+
+@pytest.fixture()
+def get_post_processor() -> Callable[[str], str]:
+    def append_the_end(text: str) -> str:
+        return text + "THE END!"
+
+    return append_the_end
+
+
+@pytest.fixture()
+def fake_json_response() -> list[dict[str, Any]]:
+    return [
+        {
+            "type": "Title",
+            "element_id": "b7f58c2fd9c15949a55a62eb84e39575",
+            "text": "LayoutParser: A Unified Toolkit for Deep Learning Based Document"
+            "Image Analysis",
+            "metadata": {
+                "languages": ["eng"],
+                "page_number": 1,
+                "filename": "layout-parser-paper.pdf",
+                "filetype": "application/pdf",
+            },
+        },
+        {
+            "type": "UncategorizedText",
+            "element_id": "e1c4facddf1f2eb1d0db5be34ad0de18",
+            "text": "1 2 0 2",
+            "metadata": {
+                "languages": ["eng"],
+                "page_number": 1,
+                "parent_id": "b7f58c2fd9c15949a55a62eb84e39575",
+                "filename": "layout-parser-paper.pdf",
+                "filetype": "application/pdf",
+            },
+        },
+    ]
+
+
+@pytest.fixture()
+def fake_multiple_docs_json_response() -> list[dict[str, Any]]:
+    return [
+        {
+            "type": "Title",
+            "element_id": "b7f58c2fd9c15949a55a62eb84e39575",
+            "text": "LayoutParser: A Unified Toolkit for Deep Learning Based Document"
+            " Image Analysis",
+            "metadata": {
+                "languages": ["eng"],
+                "page_number": 1,
+                "filename": "layout-parser-paper.pdf",
+                "filetype": "application/pdf",
+            },
+        },
+        {
+            "type": "NarrativeText",
+            "element_id": "3c4ac9e7f55f1e3dbd87d3a9364642fe",
+            "text": "6/29/23, 12:16\u202fam - User 4: This message was deleted",
+            "metadata": {
+                "filename": "whatsapp_chat.txt",
+                "languages": ["eng"],
+                "filetype": "text/plain",
+            },
+        },
+    ]

libs/partners/unstructured/tests/unit_tests/test_imports.py

@@ -0,0 +1,10 @@
+from langchain_unstructured import __all__
+
+EXPECTED_ALL = [
+    "UnstructuredLoader",
+    "__version__",
+]
+
+
+def test_all_imports() -> None:
+    assert sorted(EXPECTED_ALL) == sorted(__all__)