Returns the percentage of votes cast for this poll option in
        relation to all of its poll's other options.

def percentage(self):
        """
        Returns the percentage of votes cast for this poll option in
        relation to all of its poll's other options.
        """
        total_vote_count = self.poll.vote_count
        if total_vote_count:
            return self.vote_count * 100.0 / total_vote_count
        return 0