code: def contrast(self, level):
          
          assert(0 <= level <= 255)
          self.command(self._const.SETCONTRAST, level)
docs: Switches the display contrast to the desired level, in the range
          0-255. Note that setting the level to a low (or zero) value will
          not necessarily dim the display to nearly off. In other words,
          this method is **NOT** suitable for fade-in/out animation.
  
          :param level: Desired contrast level in the range of 0-255.
          :type level: int