How to use the enchannel-zmq-backend.createIOPubSubject function in enchannel-zmq-backend

};

      const childMessages = shell.filter(isChildMessage.bind(completeRequest));

      const completeReply = childMessages
                              .filter(msg => msg.header.msg_type === 'complete_reply')
                              .map(msg => msg.content);

      completeReply.subscribe(content => {
        callback(null, [content.matches, line]);
      });

      shell.next(completeRequest);
    });

    const iopub = enchannel.createIOPubSubject(identity, c.config);

    marked.setOptions({
      renderer: new TerminalRenderer(),
    });

    var counter = 1;

    rl.setPrompt(chalk.blue(`ick${langInfo.file_extension}:${counter}> `));
    rl.prompt();

    // Instantiate a string buffer for accumulating incomplete code strings
    var buffer = "";

    rl.on('line', (line) => {
      const isCompleteRequest = createMessage('is_complete_request');
      isCompleteRequest.content = {