[Misc] Fix circular import in vllm.transformers_utils.config

[yeqcharlotte]

Summary:
Fixes circular import error introduced by upstream vLLM PR #29966 which added a module-level import that creates a circular dependency chain which causes the following errors:

cannot import name 'ConfigFormat' from partially initialized module

This circular import happens because:

  vllm/transformers_utils/config.py
    → imports from vllm.config.utils
    → requires vllm/config/__init__.py to execute first (Python package rule)
    → which imports from vllm.config.model
    → which imports from vllm.transformers_utils.config
    → DEADLOCK: transformers_utils/config can't finish initializing!

Test Plan:

• The tests with following errors now pass: "cannot import name 'ConfigFormat' from partially initialized module"

Differential Revision: D88549243

[gemini-code-assist]

Code Review

This pull request effectively resolves a circular import issue in vllm.transformers_utils.config.py. By moving the import of getattr_iter from the module level to inside the patch_rope_parameters function, the import is deferred until runtime, which correctly breaks the dependency cycle. This is a standard and appropriate solution for this type of problem. The change is well-contained and correct, and I have no further suggestions.