make transformer fix backward compatible

[shanjiaz]

SUMMARY:
Use similar logic in the code base to determine which kv parameter name to use.

TEST PLAN:
Tested locally, kv cache tests pass : )

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[gemini-code-assist]

Summary of Changes

Hello @shanjiaz, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a robust mechanism to handle variations in key-value cache parameter naming within the transformers library. By dynamically adapting to the expected parameter name, it ensures that the system remains compatible across different library versions, thereby preventing potential runtime errors related to KV cache access.

Highlights

• KV Cache Compatibility: Implemented logic to dynamically determine the correct KV cache parameter name (past_key_values or past_key_value) based on the module's forward signature.
• Backward Compatibility: Ensures that the transformer fix remains backward compatible with different versions of the transformers library, preventing KV cache errors.

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[gemini-code-assist]

Code Review

This pull request introduces a backward-compatible way to handle the past_key_values parameter by inspecting the model's forward signature. This is a good improvement for compatibility with different transformers versions. My review includes a suggestion to optimize the implementation by caching the result of inspect.signature to avoid performance overhead during calibration, and to clarify a misleading comment.

[dsikka]

Thanks, definitely need to support older transformers versions that we’ve pinned

[dsikka]

If this ready for rereview?

[brian-dellabetta]

I think this makes sense. Can new fields be added to a module with module.x = y? If tests pass, this should be fine to land

[fynnsu]

Yeah makes sense.

My only concern is that this might not work with a module that uses **kwargs instead of explicitly listing past_key_values in the signature. That being said this might be okay if there isn't a good alternative.

However I would suggest that we make the new value past_key_values the "default". i.e. check if past_key_value is in the signature and if not we use past_key_values