code: def restore(self, drop=0):
          
          assert(drop >= 0)
          while drop > 0:
              self._savepoints.pop()
              drop -= 1
  
          img = self._savepoints.pop()
          self.display(img)
docs: Restores the last savepoint. If ``drop`` is supplied and greater than
          zero, then that many savepoints are dropped, and the next savepoint is
          restored.
  
          :param drop:
          :type drop: int