[sglang] fix: Qwen VLM Baseline

[zhaochenyang20]

What does this PR do?

This PR fix the script in https://github.com/volcengine/verl/blob/main/examples/grpo_trainer/run_qwen2_5_vl-7b.sh

The core issue was TypeError: 'NoneType' object is not callable which occurred because the variable flash_attn_varlen_func was assigned None. This happened when the primary import from transformers.modeling_flash_attention_utils failed.

I add a nested try...except block to first attempt the import from transformers, and if that fails, to then try importing flash_attn_varlen_func directly from the flash_attn package as a solution.

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I added a new test script here:

examples/grpo_trainer/run_qwen2_5_vl-7b-sglang.sh

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# Add code snippet or script demonstrating how to use this

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[gemini-code-assist]

Code Review

This pull request fixes a script for the Qwen VLM baseline and updates the flash attention handling in qwen2_vl.py. My review focuses on improving the robustness and correctness of the Python code changes. I've identified a critical issue with logging that would cause a runtime error and a high-severity issue with overly broad exception handling that could mask bugs. The new shell script appears correct.

[hiyouga]

please add another try except here