[Bugfix] Fix incorrect import of CacheConfig

[DarkLight1337]

Purpose

#21088 incorrectly imports the deprecated CacheConfig from transformers library instead of vLLM, which breaks Whisper model (and any models that use Whisper vLLM impl as encoder) when using latest transformers version.

FIX https://buildkite.com/vllm/ci/builds/30279/steps/canvas?sid=019936ef-4094-4ebf-85c3-047098b7a6ee

Test Plan

Test Result

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• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
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[gemini-code-assist]

Code Review

This pull request correctly fixes an incorrect import of CacheConfig in vllm/attention/layers/cross_attention.py. The change replaces the import from the transformers library with the correct one from vllm.config. The implementation is clean and directly addresses the bug described. I have no further comments.

[heheda12345]

Sorry. Same problem happened again. #23459
Is there a way to avoid that?

[DarkLight1337]

Once we upgrade vLLM's transformers version, mypy should be able to detect the missing import

[hmellor]

Small nit but canonical imports are preferred

Suggested change

	from vllm.config import CacheConfig, VllmConfig
	from vllm.config import VllmConfig
	from vllm.config.cache import CacheConfig

[DarkLight1337]

Let's address this separately

[russellb]

sorry, and thank you!