need help with 'chance scoring'

class YatzyScoresheet:
    def score_ones(self, hand):
        return sum(hand.ones)

    def score_chance(self, hand):
        return sum(hand)

    def score_yatzy(self, hand):
        if len(hand) == 5:
            for die in hand:
                dievalue = int(die)
                if sum(hand) == (dievalue * 5):
                    return 50
        return 0

    def _score_set(self, hand, set_size):
        scores = [0]
        for worth, count in hand._sets.items():
            if count == set_size:
                scores.append(worth*set_size)
        return max(scores)

    def score_one_pair(self, hand):
        return self._score_set(hand, 2)