[misc] fix: model reassign to inner model in vllm patch file

[ccclyu]

What does this PR do?

The model has been re-assigned to its inner model model.model so it does not have layers . fixed the reassign issue and refactor the code logic.

verl/verl/utils/vllm/patch.py

Lines 83 to 87 in f50e5c2

	model = getattr(model, "model", None) or getattr(model, "language_model", None)
	if model is None:
	raise ValueError("The provided model does not have a valid 'model' or 'language_model' attribute.")
	for layer in model.layers:

Checklist Before Starting

• Search for similar PRs. Paste at least one query link here: Current MLP_ATTR_MAPPING dictionary is wrong. #2834
• Format the PR title as [{modules}] {type}: {description} (This will be checked by the CI)
  • {modules} include fsdp, megatron, sglang, vllm, rollout, trainer, ci, training_utils, recipe, hardware, deployment, ray, worker, single_controller, misc, perf, model, algo, env, tool, ckpt, doc, data
  • If this PR involves multiple modules, separate them with , like [megatron, fsdp, doc]
  • {type} is in feat, fix, refactor, chore, test
  • If this PR breaks any API (CLI arguments, config, function signature, etc.), add [BREAKING] to the beginning of the title.
  • Example: [BREAKING][fsdp, megatron] feat: dynamic batching

Design & Code Changes

Demonstrate the high-level design if this PR is complex, and list the specific changes.

Checklist Before Submitting

Important

Please check all the following items before requesting a review, otherwise the reviewer might deprioritize this PR for review.

• Read the Contribute Guide.
• [x ] Apply pre-commit checks: pre-commit install && pre-commit run --all-files --show-diff-on-failure --color=always
• Add / Update the documentation.
• Add unit or end-to-end test(s) to the CI workflow to cover all the code. If not feasible, explain why: ...
• Once your PR is ready for CI, send a message in the ci-request channel in the verl Slack workspace. (If not accessible, please try the Feishu group (飞书群).)

[gemini-code-assist]

Code Review

This pull request correctly fixes a bug where type(model) was being used after the model variable had been reassigned to an inner model, causing issues with attribute lookups. The fix involves storing the original model type before this reassignment. The changes also include beneficial refactoring that improves code robustness and efficiency. My review includes one high-severity comment to address a potential issue where subclasses of supported models might not be handled correctly, with a suggestion to use the method resolution order (MRO) for a more robust implementation.