[docs] [issue40006] enum: Add documentation for _create_pseudo_member_ and composite members

Change by Karthikeyan Singaravelan <tir.karthi@gmail.com>: ---------- nosy: +barry, eli.bendersky, ethan.furman _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue40006> _______________________________________