def slaveof(self, host=None, port=None):
        """
        Set the server to be a replicated slave of the instance identified
        by the ``host`` and ``port``. If called without arguments, the
        instance is promoted to a master instead.
        """
        if host is None and port is None:
            return self.execute_command('SLAVEOF', Token.get_token('NO'),
                                        Token.get_token('ONE'))
        return self.execute_command('SLAVEOF', host, port)