code: def _get_average_time_stamp(action_set):
          
          # This is the average value of the iteration counter upon the most
          # recent update of each rule in this action set.
          total_time_stamps = sum(rule.time_stamp * rule.numerosity
                                  for rule in action_set)
          total_numerosity = sum(rule.numerosity for rule in action_set)
          return total_time_stamps / (total_numerosity or 1)
docs: Return the average time stamp for the rules in this action
          set.