Message 365922 - Python tracker

If object A owns a strong reference to object B, and A participates in cyclic gc, and B may be part of a cycle, then it's necessary and sufficient that A's type's tp_traverse implementation invoke Py_VISIT() passing A's pointer to B.

It would be a Really Bad Idea to add special cases to the gc module to spare some specific type(s) from following that (currently) utterly uniform rule.