code: def calibrate_white(self):
          
          (self.red_max, self.green_max, self.blue_max) = self.raw
docs: The RGB raw values are on a scale of 0-1020 but you never see a value
          anywhere close to 1020.  This function is designed to be called when
          the sensor is placed over a white object in order to figure out what
          are the maximum RGB values the robot can expect to see.  We will use
          these maximum values to scale future raw values to a 0-255 range in
          rgb().
  
          If you never call this function red_max, green_max, and blue_max will
          use a default value of 300.  This default was selected by measuring
          the RGB values of a white sheet of paper in a well lit room.
  
          Note that there are several variables that influence the maximum RGB
          values detected by the color sensor
          - the distance of the color sensor to the white object
          - the amount of light in the room
          - shadows that the robot casts on the sensor