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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _publish_connection(self, name=None):
 """Return the connection to publish. If the name is not specified, the connection associated with the current message is returned. :param str name: :rtype: rejected.process.Connection """

        try:
            conn = self._connections[name or self._message.connection]
        except KeyError:
            raise ValueError('Channel {} not found'.format(name))
        if not conn.is_connected or conn.channel.is_closed:
            raise RabbitMQException(conn.name, 599, 'NOT_CONNECTED')
        return conn