Python C API: how to mark a type as subclass of another type

[Marco Sulla]

I have two types declared as

PyTypeObject PyX_Type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)

etc.

How can I mark one of the types as subclass of the other one? I tried
to use tp_base but it didn't work.
-- 
https://mail.python.org/mailman/listinfo/python-list