GH-40282: [Python] Use C++ type traits for is_nested function

[llama90]

Rationale for this change

Use C++ type traits for is_nested function to avoid redefining in Python

What changes are included in this PR?

Expose is_nested function

Are these changes tested?

Yes

Are there any user-facing changes?

Yes

• GitHub Issue: [Python] Use C++ type traits for nested types in types.py #40282

[github-actions]

⚠️ GitHub issue #40282 has been automatically assigned in GitHub to PR creator.

[llama90]

@danepitkin Hello.

Does this align with the original intent? I closed the previous PR because there were too many code changes, and I've opened a new one.

Please review it when you have time. Thank you!

[llama90]

@AlenkaF @pitrou Does this align with the original intent? Please review it when you have time. Thank you!

[thisisnic]

Thank you for your contribution. Unfortunately, this
pull request has been marked as stale because it has had no activity in the past 365 days. Please remove the stale label
or comment below, or this PR will be closed in 14 days. Feel free to re-open this if it has been closed in error. If you
do not have repository permissions to reopen the PR, please tag a maintainer.

[AlenkaF]

Sorry for not responding to you contribution of such a long time @llama90!
I only have two suggestions otherwise the changes look good to me.

Would you be able to add changes? Otherwise I can push and merge. Thanks!

[AlenkaF]

Suggested change

	def _is_nested(data_type):
	return is_nested(data_type.id)
	def _is_nested(data_type):
	# This is simply a redirect, the official API is in pyarrow.types.
	return is_nested(data_type.id)

[AlenkaF]

I think we can simply add is_nested together with is_primitive and is_numeric here:

https://github.com/apache/arrow/blob/a15803601f439b110ba676fa5ba28473e50f50bc/python/pyarrow/includes/libarrow.pxd#L205C12-L206

Can't make this comment in form of a suggestion though, which would help finalising this PR faster.

[thisisnic]

@AlenkaF - I had Claude rebase and apply your changes, mind giving it another review if CI is happy?

[Copilot]

Copilot review overview

🟡 Changes recommended

The new lib._is_nested wrapper’s parameter handling is inconsistent with existing typed trait wrappers (e.g., _is_primitive) and should be adjusted for maintainability and consistency.

Review effort: Lite
Findings: 2

Open (2)

• Avoid Python attribute lookup in _is_nested · New
• Pass Type directly to _is_nested helper · New

What changed in this PR

This PR updates pyarrow.types.is_nested() to delegate to Arrow C++ type traits (arrow::is_nested) instead of maintaining a Python-side _NESTED_TYPES set, aligning Python behavior with the C++ definition.

Changes:

• Replace Python _NESTED_TYPES membership check with a call into pyarrow.lib for is_nested.
• Add a new Cython-level helper (lib._is_nested) in types.pxi to expose the C++ trait to Python.
• Declare arrow::is_nested(Type) in libarrow.pxd so it can be called from Cython.

File	Description
python/​pyarrow/​types.py	Switch is_nested implementation from Python set membership to pyarrow.lib call.
python/​pyarrow/​types.pxi	Add lib._is_nested wrapper to reach the C++ is_nested trait.
python/​pyarrow/​includes/​libarrow.pxd	Expose arrow::is_nested(Type) to Cython.

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[Copilot]

Copilot review overview

🟢 Approval recommended

The change is a low-risk refactor to reuse the existing C++ trait and existing Python tests already exercise types.is_nested() for nested and non-nested types.

Review effort: Lite
Findings: None

Resolved since last review (2)

• Pass Type directly to _is_nested helper
• Avoid Python attribute lookup in _is_nested

[AlenkaF]

Yes, this looks good. Thanks for finalizing it @thisisnic!