I tried to randomly assign the subjects to different treatment groups with different questions. The game had multiple rounds, so I referred to the example files on the oTree hub and upgraded otree with the pip3 install -U otree command. However, when debugging locally it keeps showing the error of the title. Here is the code:

def creating_session(subsession: Subsession):
    import itertools
    randoms = itertools.cycle([True, False])
    if subsession.round_number == 1:
        for player in subsession.get_players():
            participant = player.participant
            participant.treatment = next(randoms)
            if participant.treatment:
                participant.PAYOFFA11 = C.PAYOFF_A11u
                participant.PAYOFFA12 = C.PAYOFF_A12u
                participant.PAYOFFA21 = C.PAYOFF_A21u
                participant.PAYOFFA22 = C.PAYOFF_A22u
                participant.PAYOFFB11 = C.PAYOFF_B11u
                participant.PAYOFFB12 = C.PAYOFF_B12u
                participant.PAYOFFB21 = C.PAYOFF_B21u
                participant.PAYOFFB22 = C.PAYOFF_B22u
                participant.OtherChoice = C.OtherChoiceu
            else:
                randseed = random.random()
                participant.PAYOFFA11 = payoff_shuffle(C.PAYOFF_A11r, randseed)
                participant.PAYOFFA12 = payoff_shuffle(C.PAYOFF_A12r, randseed)
                participant.PAYOFFA21 = payoff_shuffle(C.PAYOFF_A21r, randseed)
                participant.PAYOFFA22 = payoff_shuffle(C.PAYOFF_A22r, randseed)
                participant.PAYOFFB11 = payoff_shuffle(C.PAYOFF_B11r, randseed)
                participant.PAYOFFB12 = payoff_shuffle(C.PAYOFF_B12r, randseed)
                participant.PAYOFFB21 = payoff_shuffle(C.PAYOFF_B21r, randseed)
                participant.PAYOFFB22 = payoff_shuffle(C.PAYOFF_B22r, randseed)
                participant.OtherChoice = payoff_shuffle(C.OtherChoicer, randseed)
                
class Player(BasePlayer):
    option1 = models.BooleanField(
        choices=[[True, 'Option1'], [False, 'Option2']],
        doc="""This player's decision""",
        widget=widgets.RadioSelect,
    )

    treatment = models.BooleanField()
    PAYOFFA11 = models.CurrencyField()
    PAYOFFA12 = models.CurrencyField()
    PAYOFFA21 = models.CurrencyField()
    PAYOFFA22 = models.CurrencyField()
    PAYOFFB11 = models.CurrencyField()
    PAYOFFB12 = models.CurrencyField()
    PAYOFFB21 = models.CurrencyField()
    PAYOFFB22 = models.CurrencyField()
    OtherChoice = models.CurrencyField()
    
    
The page code:

class Decision(Page):
    form_model = 'player'
    form_fields = ['option1']
    def vars_for_template(self):
        participant = Player.participant
        return {
            'round_number': self.round_number,
            'payoffA11': participant.PAYOFF_A11[self.round_number - 1],
            'payoffA12': participant.PAYOFF_A12[self.round_number - 1],
            'payoffB11': participant.PAYOFF_B11[self.round_number - 1],
            'payoffB12': participant.PAYOFF_B12[self.round_number - 1],
            'payoffA21': participant.PAYOFF_A21[self.round_number - 1],
            'payoffB21': participant.PAYOFF_B21[self.round_number - 1],
            'payoffA22': participant.PAYOFF_A22[self.round_number - 1],
            'payoffB22': participant.PAYOFF_B22[self.round_number - 1],
            'treatment': participant.treatment
        }
 Please help!