text: def strategy(history, memory):
      """
      Defect every few turns, based on the fibonacci sequence.
      i.e., defect turn 2 (1), turn 3 (1), turn 5 (2), turn 8 (3), turn 13 (5)
      """
      if memory is None:
          last_defection_turn = 0
          prev_fibonacci = 1
          current_fibonacci = 1
      else:
          last_defection_turn, prev_fibonacci, current_fibonacci = memory
  
      if history.shape[1] == last_defection_turn + current_fibonacci:
          last_defection_turn = history.shape[1]
          next_fibonacci = prev_fibonacci + current_fibonacci
          prev_fibonacci = current_fibonacci
          current_fibonacci = next_fibonacci
          choice = 0
      else:
          choice = 1
  
      return choice, (last_defection_turn, prev_fibonacci, current_fibonacci)
  