[bugfix] Lazy import cv2

[angelayi]

Purpose

Fixes pytest -sv tests/standalone_tests/lazy_imports.py failure which I saw in this run

Test Plan

pytest -sv tests/standalone_tests/lazy_imports.py

Test Result

test passes

cc @ProExpertProg

[gemini-code-assist]

Code Review

This pull request correctly implements lazy loading for the cv2 module to fix a test failure. The current approach of moving the import into each function that uses it is valid. However, I've suggested using the LazyLoader utility, which is a more idiomatic and maintainable pattern within the vLLM codebase for handling lazy dependencies. This centralizes the lazy-loading logic and avoids repetitive import statements in functions. My review includes a concrete suggestion to adopt this pattern.

[gemini-code-assist]

Instead of moving the cv2 import inside each function, consider using the LazyLoader utility from vllm.utils. This is a cleaner and more idiomatic approach for lazy loading in this project, as seen with other modules. It avoids repeating import statements and keeps the function bodies cleaner, while still achieving the goal of lazy loading.

Suggested change

	import cv2
	from vllm.utils import LazyLoader
	cv2 = LazyLoader("cv2", globals(), "cv2")

[gemini-code-assist]

With the proposed LazyLoader at the module level, this local import is no longer necessary and can be removed.