class Screen(object):    __slots__ = ('__width', '__height', '__resolution')    def __init__(self):        self.__width, self.__height, self.__resolution = None, None, None    @property    def width(self):        return self.__width    @width.setter    def width(self, value):        if not isinstance(value, (int, float)):            raise ValueError('width must be float')        elif value < 0:            raise ValueError('width cant\'t be smaller than 0')        else:            self.__width = value    @property    def height(self):        return self.__height    @height.setter    def height(self, value):        if not isinstance(value, (int, float)):            raise ValueError('width must be float')        elif value < 0:            raise ValueError('width cant\'t be smaller than 0')        else:            self.__height = value    @property    def resolution(self):        self.__resolution = self.__height * self.__width        return self.__resolution