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# dogs.py

from datetime import date

from typing import Type, TypeVar

TAnimal = TypeVar("TAnimal", bound="Animal")

class Animal:

def __init__(self, name: str, birthday: date) -> None:

self.name = name

self.birthday = birthday

@classmethod

def newborn(cls: Type[TAnimal], name: str) -> TAnimal:

return cls(name, date.today())

def twin(self: TAnimal, name: str) -> TAnimal:

cls = self.__class__

return cls(name, self.birthday)

class Dog(Animal):

def bark(self) -> None:

print(f"{self.name} says woof!")

fido = Dog.newborn("Fido")

pluto = fido.twin("Pluto")

fido.bark()

pluto.bark()