code: def add(self, observation, action, reward, terminal, *args):
      
      # If this will be a problem for maintenance, we could probably override
      # DQNAgent.add() method instead.
      artificial_done = self._artificial_done and terminal
      args = list(args)
      args.append(artificial_done)
      return super(_OutOfGraphReplayBuffer, self).add(observation, action, reward,
                                                      terminal, *args)
docs: Append artificial_done to *args and run parent method.