feat: implement to_arrow for cuDF

[LiamConnors]

What type of PR is this? (check all applicable)

• 💾 Refactor
• ✨ Feature
• 🐛 Bug Fix
• 🔧 Optimization
• 📝 Documentation
• ✅ Test
• 🐳 Other

Related issues

• Related issue # test: Get all cuDF tests passing #862
• Closes #

Checklist

• Code follows style guide (ruff)
• Tests added
• Documented the changes

If you have comments or can explain your changes, please do so below.

[MarcoGorelli]

thanks @LiamConnors !

looking at the cuDF docs again, I think we can implement this one

we can modify

narwhals/narwhals/_pandas_like/dataframe.py

Lines 679 to 681 in b32fd4a

	if self._implementation is Implementation.CUDF: # pragma: no cover
	msg = "`to_arrow` is not implemented for CuDF backend."
	raise NotImplementedError(msg)

to return self._native_frame.to_arrow(preserve_index=False) (see https://docs.rapids.ai/api/cudf/stable/user_guide/api_docs/api/cudf.dataframe.to_arrow/#cudf.DataFrame.to_arrow)

If we do that, then I think these tests won't need xfailing

[LiamConnors]

Thanks @MarcoGorelli! I've updated the PR and the tests pass in the notebook now

[MarcoGorelli]

awesome, thanks @LiamConnors ! 🙌