code: def set_contrast(self, contrast):
          
          if contrast < 0 or contrast > 255:
              raise ValueError('Contrast must be a value from 0 to 255 (inclusive).')
          self.command(SSD1306_SETCONTRAST)
          self.command(contrast)
docs: Sets the contrast of the display.  Contrast should be a value between
          0 and 255.