> I still don't understand why you need _abc_data.
I'm using it both for comparisons which needed to build an abstract base class and typing. Currently there are 2 ways, i need to create a dummy abc and put type() calls everywhere or i need to set a constant to my module and _abc_data is totally irrelevant with this. I dont think users want that.

> On the other hand, _abc_data is implementation detail of extension module, not interpreter.
Abstract base classes can be called a core part of python too and when someone needs to obtain type of the struct that holds state of ABCs it shouldnt be hard, types module should expose it.