`PySequence_In` is not documented

Documentation

PySequence_In is part of the limited C-API, and has no document. PEP 3100 ( https://peps.python.org/pep-3100/ ) says this function is "To be removed," but it has not been removed in the latest version, so documentation seems to be needed.

Linked PRs

• gh-127896: Add missing document of PySequence_In #127979

[ZeroIntensity]

New applications shouldn't use it, we just keep it for the limited API. I'm not sure we need to encourage more usage by documenting it.

[encukou]

It's exactly equivalent to PySequence_Contains.

The docs should mention that it's deprecated, and show the preferred spelling.

If this function is deprecated, should we add Py_DEPRECATED to the declaration?
https://github.com/python/cpython/blob/main/Include/abstract.h#L773

[ZeroIntensity]

No idea what the precedent is here, but I suspect that it should be soft deprecated for compatibility reasons.

[skirpichev]

The docs should mention that it's deprecated, and show the preferred spelling.

Formally, it's not deprecated yet;)

I suspect that it should be soft deprecated for compatibility reasons.

Maybe not. Search on the Github shows only few projects, which use this. On another hand, support this has 0 maintenance burden.