use pytest.mark directly

[ydshieh]

What does this PR do?

#25598 uses from pytest import mark which breaks the function get_test_classes as the test module would have mark as attribute, and

getattr(attr_value, "all_model_classes", [])

gives an 'MarkDecorator' object (while attr_value is the pytest.mark).

This PR import pytest and use @pytest.mark to avoid the issue.

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[amyeroberts]

Would just using pytest.mark.flash_attn_test instead of importing from pytest import mark work? This looks like a complex workaround for a feature which is just a nice-to-have e.g. (comments here and here)

[ydshieh]

Thanks for the great suggestion ! It works, and I will apply the same changes to all related test files.

[amyeroberts]

Thanks for fixing!