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langchain: Update ContextualCompressionRetriever base_retriever type to RetrieverLike (#24192)

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**Description:**
When initializing retrievers with `configurable_fields` as base
retriever, `ContextualCompressionRetriever` validation fails with the
following error:

```
ValidationError: 1 validation error for ContextualCompressionRetriever
base_retriever
  Can't instantiate abstract class BaseRetriever with abstract method _get_relevant_documents (type=type_error)
```

Example code:

```python
esearch_retriever = VertexAISearchRetriever(
    project_id=GCP_PROJECT_ID,
    location_id="global",
    data_store_id=SEARCH_ENGINE_ID,
).configurable_fields(
    filter=ConfigurableField(id="vertex_search_filter", name="Vertex Search Filter")
)

# rerank documents with Vertex AI Rank API
reranker = VertexAIRank(
    project_id=GCP_PROJECT_ID,
    location_id=GCP_REGION,
    ranking_config="default_ranking_config",
)

retriever_with_reranker = ContextualCompressionRetriever(
    base_compressor=reranker, base_retriever=esearch_retriever
)
```

It seems like the issue stems from ContextualCompressionRetriever
insisting that base retrievers must be strictly `BaseRetriever`
inherited, and doesn't take into account cases where retrievers need to
be chained and can have configurable fields defined.


0a1e475a30/libs/langchain/langchain/retrievers/contextual_compression.py (L15-L22)

This PR proposes that the base_retriever type be set to `RetrieverLike`,
similar to how `EnsembleRetriever` validates its list of retrievers:


0a1e475a30/libs/langchain/langchain/retrievers/ensemble.py (L58-L75)
This commit is contained in:
Sheng Han Lim 2024-07-22 02:23:19 +08:00 committed by GitHub
parent d98b830e4b
commit 0c6a3fdd6b
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1 changed files with 2 additions and 2 deletions
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4
libs/langchain/langchain/retrievers/contextual_compression.py
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@ -5,7 +5,7 @@ from langchain_core.callbacks import (
CallbackManagerForRetrieverRun,
)
from langchain_core.documents import Document
from langchain_core.retrievers import BaseRetriever
from langchain_core.retrievers import BaseRetriever, RetrieverLike
from langchain.retrievers.document_compressors.base import (
BaseDocumentCompressor,
@ -18,7 +18,7 @@ class ContextualCompressionRetriever(BaseRetriever):
base_compressor: BaseDocumentCompressor
"""Compressor for compressing retrieved documents."""
base_retriever: BaseRetriever
base_retriever: RetrieverLike
"""Base Retriever to use for getting relevant documents."""
class Config: