Small improvement to great value in AmazonKnowledgeBasesRetriever: Get all metadata

[alexol91]

Checked

• I searched existing ideas and did not find a similar one
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• I've clearly described the feature request and motivation for it

Feature request

AWS Knowledge Bases allows you to create documents with metadata and langchain allows you to filter by them (this is great!)

The problem we encountered is that this metadata is not returned as part of the response.

I've been reviewing the Bedrock documentation and Langchain source code with AWS engineers and supporting this would be very easy.

Motivation

The reason for this request is to be able to obtain all the metadata of the knowledge base, something highly useful for our agents and systems based on langchain.

Proposal (If applicable)

According to the AWS documentation (https://docs.aws.amazon.com/bedrock/latest/APIReference/API_agent-runtime_Retrieve.html), in their response they offer the metadata object with the JSON that I am looking for.

{ "nextToken": "string", "retrievalResults": [ { "content": { "text": "string" }, "location": { "s3Location": { "uri": "string" }, "type": "string" }, "metadata": { "string" : JSON value }, "score": number } ] }

In LangChain you can see the code:
Document( page_content=result["content"]["text"], metadata={ "location": result["location"], "score": result["score"] if "score" in result else 0, }, )

You would only have to add the line:
"metadata": result["metadata"],

Document( page_content=result["content"]["text"], metadata={ "location": result["location"], "metadata": result["metadata"], "score": result["score"] if "score" in result else 0, }, )

or
Document( page_content=result["content"]["text"], metadata={ "location": result["location"], "score": result["score"] if "score" in result else 0, **result["metadata"] }, )

[karlnewell]

PR to address this feature request, langchain-ai/langchain-aws#36