Python3 interfaces plaything

fun.py

from abc import ABC, abstractmethod

class InterfaceA(ABC):
    @abstractmethod
    def method_a(self) -> None: ...

class InterfaceB(ABC):
    @abstractmethod
    def method_b(self) -> None: ...

class InterfaceAB(InterfaceA, InterfaceB): pass

class ClassA(InterfaceA):
    def method_a(self) -> None:
        print("a")

class ClassB(InterfaceB):
    def method_b(self: 'InterfaceAB') -> None:
        print("b")
        self.method_a()

class AB(ClassA, ClassB): pass

ab = AB()
ab.method_b()