fix(langchain): update docstring for trace_context

[hassiebp]

Update LangchainCallbackHandler docstring to document trace_context and provide an example for setting a custom trace ID.

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Important

Update LangchainCallbackHandler docstring to document trace_context and provide an example for setting a custom trace ID.

• Documentation:
  • Update LangchainCallbackHandler docstring to include trace_context parameter.
  • Provide example for setting a custom trace ID in LangchainCallbackHandler.

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Disclaimer: Experimental PR review

Greptile Overview

Greptile Summary

Enhanced documentation for LangchainCallbackHandler by adding the missing trace_context parameter description and usage example. The docstring now clearly explains how to set custom trace IDs for distributed tracing or linking LangChain runs to upstream systems.

Confidence Score: 5/5

• This PR is safe to merge with no risk
• This is a documentation-only change that adds missing parameter documentation and a usage example. No code logic was modified, only docstrings were enhanced. The documentation accurately reflects the existing functionality.
• No files require special attention

Important Files Changed

File Analysis

Filename	Score	Overview
langfuse/langchain/CallbackHandler.py	5/5	Added comprehensive documentation for trace_context parameter with clear example showing custom trace ID usage

Sequence Diagram

sequenceDiagram
    participant User
    participant CallbackHandler
    participant Langfuse Client
    participant Trace

    User->>CallbackHandler: Initialize with trace_context={"trace_id": "custom-id"}
    Note over CallbackHandler: Store trace_context parameter
    
    User->>CallbackHandler: Execute LangChain chain
    CallbackHandler->>Langfuse Client: start_observation(trace_context=trace_context)
    Langfuse Client->>Trace: Create/link to trace with custom ID
    Note over Trace: Trace uses custom trace_id<br/>from trace_context
    Trace-->>Langfuse Client: Trace created/linked
    Langfuse Client-->>CallbackHandler: Observation started
    CallbackHandler-->>User: Chain execution continues

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