code: def update(self):
          
          if self.var_info.bits_per_pixel == 1:
              b = self._img.tobytes("raw", "1;R")
              self.mmap[:len(b)] = b
  
          elif self.var_info.bits_per_pixel == 16:
              self.mmap[:] = self._img_to_rgb565_bytes()
  
          elif self.var_info.bits_per_pixel == 32:
              self.mmap[:] = self._img.convert("RGB").tobytes("raw", "XRGB")
  
          else:
              raise Exception("Not supported - platform %s with bits_per_pixel %s" %
                  (self.platform, self.var_info.bits_per_pixel))
docs: Applies pending changes to the screen.
          Nothing will be drawn on the screen until this function is called.