code: def merge(self, imgs):
          
          if not imgs:
              raise ValueError('empty channel list')
          if len(imgs) == 1:
              return imgs[0]
          return Image.merge(self.mode, imgs)
docs: Merge image channels.
  
          Parameters
          ----------
          imgs : `list` of `PIL.Image.Image`
  
          Returns
          -------
          `PIL.Image.Image`
  
          Raises
          ------
          ValueError
              If image channel list is empty.