VertexAI usage metadata parsing

[ReneFabricius]

Some ChatVertexAI responses contain empty usage_metadata in generation_info while message contains valid one. Breaking here does not allow for processing of the valid one and results in returning None.

Added processing of tokens details for ChatVertexAI as they have different name and different format than the currently processed details.
Keeping the details unprocessed leads to Pydantic validation error further down the line -> langfuse/langfuse#5468

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Important

Improves usage_metadata parsing in ChatVertexAI responses by handling empty metadata and processing token details in langfuse/callback/langchain.py.

• Behavior:
  • Modified _parse_usage in langfuse/callback/langchain.py to use .get('usage_metadata', None) for safer access.
  • Prevents early termination when usage_metadata is empty in ChatVertexAI responses.
  • Processes valid metadata from message field when generation_info metadata is empty.
• Token Details:
  • Updated _parse_usage_model to handle prompt_tokens_details and candidates_tokens_details for ChatVertexAI.
  • Ensures correct parsing of token details to avoid Pydantic validation errors.

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Greptile Summary

Disclaimer: Experimental PR review

Enhanced ChatVertexAI usage metadata parsing to handle empty metadata cases and properly process token details in different formats.

• Modified _parse_usage in langfuse/callback/langchain.py to safely handle empty usage_metadata using .get() method
• Added support for extracting valid metadata from message field when generation_info metadata is empty
• Updated token details processing to handle ChatVertexAI-specific fields like prompt_tokens_details and candidates_tokens_details
• Improved Pydantic validation compatibility by properly formatting token details before validation

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[greptile-apps]

LGTM

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[greptile-apps]

LGTM

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[greptile-apps]

LGTM

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[ReneFabricius]

Hi @hassiebp , could you please look at this when you get a chance?

[hassiebp]

Thanks a lot for your contribution! Closing this in favor of #1181