@classmethod
    def get_vote(cls, card, user):
        return cls.get_by(user=user, card=card)
A purge request should result in L{PubSubResource.purge} being
dataset/ETHPy150Open Net-ng/kansha/kansha/card_addons/vote/models.py/DataVote.get_vote--crossover with--dataset/ETHPy150Open ralphm/wokkel/wokkel/test/test_pubsub.py/PubSubServiceTest.test_on_purge