class AttrGetter:

    def __getattr__(self, item):
        raise AttributeError(item)


class MixinA(AttrGetter):

    def __getattr__(self, item):
        if item == 'a':
            return 'MixinA'
return super().__getattr__(item)


class MixinB(AttrGetter):

    def __getattr__(self, item):
        if item == 'b':
            return 'MixinB'
return super().__getattr__(item)


class Example(MixinA, MixinB):
    pass
print(Example.mro())
e = Example()
print(e.a)
print(e.b)
print(e.c)
'super' object has no attribute '__getattr__' in python3