How to write class based generic python

generic.py

"""
Animal
=======
+ name
+ legs
"""


class Animal(object):
    name = None
    legs = None

    def get_name(self):
        assert self.name is not None, (
            "Any {} should have `name` attribute".format(self.__class__.__name__)
        )
        return self.name

    def get_legs(self):
        assert self.legs is not None, (
            "Any {} should have `leg` attribute".format(self.__class__.__name__)
        )

        assert self.legs > 0, (
            "Any {} should have at least 1 `leg`".format(self.__class__.__name__)
        )

        return self.legs

    def write(self):
        return "{} {}".format(self.get_name(), self.get_legs())


class Mixin(object):
    def prettify(self):
        return "{} has {} legs".format(self.get_name(), self.get_legs())


class Bird(Mixin, Animal):
    name = 'bird'
    legs = 1


bird = Bird()
bird.write()
bird.prettify()