如何在类中包含扩展

class Animal:
    def __init__(self, name):
        self.name = name

    def speak(self):
        print("Animal speaks")

class Dog(Animal):
    def __init__(self, name):
        super().__init__(name)

    def speak(self):
        print("Dog barks")

animal = Animal("Animal")
animal.speak()  # 输出: Animal speaks

dog = Dog("Dog")
dog.speak()  # 输出: Dog barks

class Flyable:
    def fly(self):
        pass

class Bird(Flyable):
    def fly(self):
        print("Bird flies")

class Airplane(Flyable):
    def fly(self):
        print("Airplane flies")

bird = Bird()
bird.fly()  # 输出: Bird flies

airplane = Airplane()
airplane.fly()  # 输出: Airplane flies