There's a typedef in methodobject.h called PyNoArgsFunction.  You might think it's used for METH_NOARGS functions--you'd be wrong, those use PyCFunction and pass in NULL for args.

No, PyNoArgsFunction is never used.  Nor is it documented.  It's found in exactly one place in the CPython tree, and that's when it's declared.  We should consider removing it.

Note that I'm pretty sure this will break external code; a quick Google found that Blender's extension interface uses it.  And AFAICT they still use it, and they *have* moved to Python 3.  So I could believe the right call is "we better leave it in".

I suspect that PyNoArgsFunction *was* used once upon a time.  I further suspect that year started with a 1.