code: def pay(self, predecessor):
          
          assert predecessor is None or isinstance(predecessor, MatchSet)
  
          if predecessor is not None:
              expectation = self._algorithm.get_future_expectation(self)
              predecessor.payoff += expectation
docs: If the predecessor is not None, gives the appropriate amount of
          payoff to the predecessor in payment for its contribution to this
          match set's expected future payoff. The predecessor argument should
          be either None or a MatchSet instance whose selected action led
          directly to this match set's situation.
  
          Usage:
              match_set = model.match(situation)
              match_set.pay(previous_match_set)
  
          Arguments:
              predecessor: The MatchSet instance which was produced by the
                  same classifier set in response to the immediately
                  preceding situation, or None if this is the first situation
                  in the scenario.
          Return: None