code: def save_plain_image_as_file(self, filepath, format='png', quality=90):
          
          img_w = self.get_plain_image_as_widget()
          # assumes that the image widget has some method for saving to
          # a file
          img_w.save(filepath, format=format, quality=quality)
docs: Used for generating thumbnails.  Does not include overlaid
          graphics.