    def on_approval(self, bigchain, new_height):
        """Override to update the database state according to the
           election rules. Consider the current database state to account for
           other concluded elections, if required.
        """
        raise NotImplementedError
Override to update the database state according to the
election rules. Consider the current database state to account for
other concluded elections, if required.
bigchaindb/elections/election.py