Python MRO and Multi-class inheritance type clobbering

mro-clobber.py

from abc import ABC, abstractmethod
from datetime import timedelta

class A1(ABC):
    _value = "A1"

    def __init__(self):
        print("A1 type at init:", type(self._value))

    def test_value(self):
        assert type(self._value) is not str

    @abstractmethod
    def print_value(self):
        pass


class A2(ABC):
    _value = timedelta()

    def __init__(self):
        pass

    def print_value(self):
        print('A2 type:', type(self._value))
        print(self._value)

class B(A1, A2):
    _value = 1

    def __init__(self):
        super().__init__()

    def print_type(self):
        print('B type:', type(self._value))

    def print_value(self):
        print('B type:', type(self._value))
        print(self._value)

def main():
    b = B()
    b.print_value()
    b.print_type()
    b.test_value()

    print(B.mro())

if __name__ == '__main__':
    main()