class adapter:
    def __init__(self, target):
        if target is None:
            raise Exception("Adapter target must not bo None.")

        self.__result = None
        self.__target = target

    @property
    def target(self):
        return self.__target
    
    @property
    def result(self):
        if self.__result is None:
            self.__result = self.__class__.convert(self.target)
            
            return self.__result

        return self.__result

    def convert(target):
        raise Exception("This function must be overwriten.")