code: def scale(self):
          
          if self.__scale:
              return self.__scale
          v = max(self.screenshot().size) / max(self.window_size())
          self.__scale = round(v)
          return self.__scale
docs: UIKit scale factor
          
          Refs:
              https://developer.apple.com/library/archive/documentation/DeviceInformation/Reference/iOSDeviceCompatibility/Displays/Displays.html