sympy__sympy-12489

combinatorics.Permutation can't be subclassed properly

Verdict: the fix is stated in the issue (Tier A).

`_af_new` should probably be a `classmethod` with creating command `Basic.__new__(cls, perm)`.

The text states the fix: “`_af_new` should probably be a `classmethod` with creating command `Basic.__new__(cls, perm)`.”