from abc import ABC, abstractmethod


# Handler
class Rescuer(ABC):
    # HandleRequest()
    def __init__(self, code, rescuer):
        self._code = code
        self._next = rescuer

    def help(self, code):
        if self._code == code:
            self.to_help()
        elif isinstance(self._next, Rescuer):
            self._next.help(code)

    @abstractmethod
    def to_help(self):
        pass


# ConcreteHandler
class Firefighter(Rescuer):
    def __init__(self, rescuer):
        super().__init__(1, rescuer)

    def to_help(self):
        print("call firefighters")


# ConcreteHandler
class Police(Rescuer):
    def __init__(self, rescuer):
        super().__init__(2, rescuer)

    def to_help(self):
        print("call the police")


# ConcreteHandler
class Ambulance(Rescuer):
    def __init__(self, rescuer):
        super().__init__(3, rescuer)

    def to_help(self):
        print("call an ambulance")


ambulance = Ambulance(0)
police = Police(ambulance)
firefighter = Firefighter(police)
firefighter.help(1)
# printed: call firefighters
firefighter.help(2)
# printed: call the police
firefighter.help(3)
# printed: call an ambulance