Add **kwargs parameter to v1 FlashAttentionImpl as catch-all

[haojin2]

Purpose

Should help #33470

Test Plan

TBA

Test Result

TBA

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[gemini-code-assist]

Code Review

This pull request adds a **kwargs parameter to FlashAttentionImpl.__init__ to act as a catch-all for unused arguments, improving forward compatibility. While this is a good practice, it can hide potential bugs from typos in argument names. I've suggested adding a warning log for any unexpected keyword arguments to make debugging easier.

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[mergify]

Hi @haojin2, the pre-commit checks have failed. Please run:

uv pip install pre-commit
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

Tip

Is mypy or markdownlint failing?

mypy and markdownlint are run differently in CI. If the failure is related to either of these checks, please use the following commands to run them locally:

# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10
# For markdownlint
pre-commit run --hook-stage manual markdownlint