def conditional_roulette_probs(history):
    """

    Example:
    conditional_roulette_probs([1, 3, 1, 5, 1])
    > {1: {3: 0.5, 5: 0.5},
       3: {1: 1.0},
       5: {1: 1.0}
      }
    """
    pass


q5.check()