code: def redo(self):
          
          controllers = self.forward()
          if controllers is None:
              ups = ()
          else:
              ups = tuple([controller.redo() for
                           controller in controllers])
          if self.process_ups is not None:
              return self.process_ups(ups)
          else:
              return ups
docs: Redo the last action.
  
          This will call `redo()` on all controllers involved in this action.