What is messaging OOP in Python

duck.py

from abc import ABC, abstractmethod
from typing import Iterable

class Soundable(ABC):
    @abstractmethod
    def sound(self) -> str:
        pass

def sound_all(soundables: Iterable[Soundable]):
    for soundable in soundables:
        print(soundable.sound())

###############################################
class Animal(ABC):
    pass

class Duck(Animal, Soundable):
    def sound(self) -> str:
        return "🦆 < quack"

class Dog(Animal, Soundable):
    def sound(self) -> str:
        return "🐕 < bow!!"

print("Animals")
sound_all([Duck(), Dog()])
# NG sound_all([Duck(), Dog(), Fish()])

###############################################
class Toy(ABC):
    pass

class ToyDuck(Toy, Soundable):
    def sound(self) -> str:
        return "🤖 < quack"

class ToyDog(Toy, Soundable):
    def sound(self) -> str:
        return "🤖 < bow!!"

print("Toys")
sound_all([ToyDuck(), ToyDog()])

###############################################
print("Mixed Soundables")
sound_all([Duck(), Dog(), ToyDuck(), ToyDog()])



###################### おまけ
# ...でももしこうなると?
class Fish(Animal):
    pass

class ToyFish(Toy):
    pass

all = [Duck(), Dog(), Fish(), ToyDuck(), ToyDog(), ToyFish()]
# list[Soundable] とは言えない

def only_soundables_of(items: Iterable) -> Iterable[Soundable]:
    return filter(lambda item: isinstance(item, Soundable), items)

print("Mixed Soundables (safer)")
sound_all(only_soundables_of(all))