This is used to implement CPython-like hashing of numeric types e.g.in Sage orin gmpy2. Actually, the same info is available viasys.hash_info, so I don't see reasons to hide this in Python.h.

See#106320 and#107026.

Linked PRs

• gh-111389: expose _PyHASH_INF/BITS/MODULUS/IMAG macros as public #111418
• gh-111389: Add PyHASH_MULTIPLIER constant #119214
• [3.13] gh-111389: Add PyHASH_MULTIPLIER constant (GH-119214) #119334
• gh-111389: replace deprecated occurrences of_PyHASH_* macros #141236