Zep Retriever - Vector Search Over Chat History (#4533)

# Zep Retriever - Vector Search Over Chat History with the Zep Long-term
Memory Service

More on Zep: https://github.com/getzep/zep

Note: This PR is related to and relies on
https://github.com/hwchase17/langchain/pull/4834. I did not want to
modify the `pyproject.toml` file to add the `zep-python` dependency a
second time.

Co-authored-by: Daniel Chalef <daniel.chalef@private.org>

tests/unit_tests/retrievers/test_zep.py

@@ -0,0 +1,111 @@
+from __future__ import annotations
+
+import copy
+from typing import TYPE_CHECKING, List
+
+import pytest
+from pytest_mock import MockerFixture
+
+from langchain.retrievers import ZepRetriever
+from langchain.schema import Document
+
+if TYPE_CHECKING:
+    from zep_python import SearchResult, ZepClient
+
+
+@pytest.fixture
+def search_results() -> List[SearchResult]:
+    from zep_python import Message, SearchResult
+
+    search_result = [
+        {
+            "message": {
+                "uuid": "66830914-19f5-490b-8677-1ba06bcd556b",
+                "created_at": "2023-05-18T20:40:42.743773Z",
+                "role": "user",
+                "content": "I'm looking to plan a trip to Iceland. Can you help me?",
+                "token_count": 17,
+            },
+            "summary": None,
+            "dist": 0.8734284910450115,
+        },
+        {
+            "message": {
+                "uuid": "015e618c-ba9d-45b6-95c3-77a8e611570b",
+                "created_at": "2023-05-18T20:40:42.743773Z",
+                "role": "user",
+                "content": "How much does a trip to Iceland typically cost?",
+                "token_count": 12,
+            },
+            "summary": None,
+            "dist": 0.8554048017463456,
+        },
+    ]
+
+    return [
+        SearchResult(
+            message=Message.parse_obj(result["message"]),
+            summary=result["summary"],
+            dist=result["dist"],
+        )
+        for result in search_result
+    ]
+
+
+@pytest.fixture
+@pytest.mark.requires("zep_python")
+def zep_retriever(
+    mocker: MockerFixture, search_results: List[SearchResult]
+) -> ZepRetriever:
+    mock_zep_client: ZepClient = mocker.patch("zep_python.ZepClient", autospec=True)
+    mock_zep_client.search_memory.return_value = copy.deepcopy(  # type: ignore
+        search_results
+    )
+    mock_zep_client.asearch_memory.return_value = copy.deepcopy(  # type: ignore
+        search_results
+    )
+    zep = ZepRetriever(session_id="123", url="http://localhost:8000")
+    zep.zep_client = mock_zep_client
+    return zep
+
+
+@pytest.mark.requires("zep_python")
+def test_zep_retriever_get_relevant_documents(
+    zep_retriever: ZepRetriever, search_results: List[SearchResult]
+) -> None:
+    documents: List[Document] = zep_retriever.get_relevant_documents(
+        query="My trip to Iceland"
+    )
+    _test_documents(documents, search_results)
+
+
+@pytest.mark.requires("zep_python")
+@pytest.mark.asyncio
+async def test_zep_retriever_aget_relevant_documents(
+    zep_retriever: ZepRetriever, search_results: List[SearchResult]
+) -> None:
+    documents: List[Document] = await zep_retriever.aget_relevant_documents(
+        query="My trip to Iceland"
+    )
+    _test_documents(documents, search_results)
+
+
+def _test_documents(
+    documents: List[Document], search_results: List[SearchResult]
+) -> None:
+    assert len(documents) == 2
+    for i, document in enumerate(documents):
+        assert document.page_content == search_results[i].message.get(  # type: ignore
+            "content"
+        )
+        assert document.metadata.get("uuid") == search_results[
+            i
+        ].message.get(  # type: ignore
+            "uuid"
+        )
+        assert document.metadata.get("role") == search_results[
+            i
+        ].message.get(  # type: ignore
+            "role"
+        )
+        assert document.metadata.get("score") == search_results[i].dist