Fix method check for partialmethod attribute

[xsro]

Thank you for maintaining such a great project!

I tested this library with the Bolts robot and encountered a small compatibility issue related to Python's partialmethod implementation.

As Python 3.10 renamed the internal _partialmethod (single underscore) to __partialmethod__ (double underscores) for stronger encapsulation of its functools.partialmethod underpinning, this causes compatibility gaps across different Python versions.

This patch addresses the issue by properly checking the parent of partialmethod to support both the old and new internal identifiers, ensuring broader Python version compatibility.

Would you consider merging this fix?

[superfashi]

Hi, thank you for the PR but unfortunately this project is right now unmaintained (I believe).

That being said, I think we could still merge your PR.

I did some test myself on Python 3.12 and it seems like functools.partialmethod still gives _partialmethod as attribute. Could you tell me what went wrong in your environment?

[xsro]

Sorry, AI tells me it changes since 3.10. I check the python's commit history and find it is updated in 3.13.0 with BOP38364. The official changelog is documented in 3.13