Fix RecursionError in MediaWithBytes unpickling

[nrghosh]

Guard __getattr__ against recursion when media attribute is not yet set during pickle deserialization. Adds regression test.

Fixes: #30818

Purpose

Fix RecursionError when unpickling MediaWithBytes dataclass, which breaks vLLM usage with Ray. The __getattr__ method recursively calls itself when self.media is not yet set during pickle deserialization.

Test Plan

pytest tests/multimodal/test_image.py::test_media_with_bytes_pickle_roundtrip -v

Test Result

Test verifies pickle roundtrip succeeds and attribute delegation works before and after unpickling. Without the fix, unpickling causes RecursionError: maximum recursion depth exceeded.

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[gemini-code-assist]

Code Review

This pull request addresses a RecursionError that occurs when unpickling MediaWithBytes objects. The root cause is the __getattr__ method recursively calling itself when the media attribute is not yet set during deserialization. The proposed fix introduces a guard to check for the presence of media in the instance's __dict__, which is a correct and idiomatic way to prevent such recursion. A comprehensive regression test is also added, which validates the fix by performing a pickle roundtrip and asserting attribute delegation works correctly before and after. The changes are well-implemented and effectively resolve the issue.

[mergify]

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