filter flash_attn optional imports loading remote code (#30954)
* filter flash_attn optional imports loading remote code
* improve pattern
* fix code style
* Update src/transformers/dynamic_module_utils.py
Co-authored-by: Matt <Rocketknight1@users.noreply.github.com>
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Co-authored-by: Matt <Rocketknight1@users.noreply.github.com>