class Screen(object):    @property    def width(self):        return self._width    @width.setter    def width(self,value):        if not isinstance(value,int):            raise ValueError('width must be integer')        if value<0:            raise ValueError('width must be greater than zero ')        self._width=value    @property    def height (self):        return self._height    @height.setter    def height (self, value):        if not isinstance(value, int):            raise ValueError('height  must be integer')        if value < 0:            raise ValueError('height  must be greater than zero ')        self._height  = value    @property    def resolution(self):        return self._height*self._width