def user_is_sponsor(self, user):
        """Return whether the given user is a sponsor of the activity.

        Returns:
            Boolean

        """
        sponsors = self.get_true_sponsors()
        for sponsor in sponsors:
            sp_user = sponsor.user
            if sp_user == user:
                return True

        return False
Return whether the given user is a sponsor of the activity.

        Returns:
            Boolean