class Base:
    __handlers = []

    @staticmethod
    def handler(cls):
        def wrapper():
            Base.add_handler(cls)

        wrapper()

    @classmethod
    def add_handler(cls, view):
        cls.__handlers.append(view)


class View:
    pass


@Base.handler
class First(View):
    pass


bot = Base()
print(bot._Base__handlers)