code: function IncomingPromise(responseStream, promiseHeaders) {
    var stream = new Readable();
    stream._read = noop;
    stream.push(null);
    stream._log = responseStream._log;
  
    IncomingRequest.call(this, stream);
  
    this._onHeaders(promiseHeaders);
  
    this._responseStream = responseStream;
  
    var response = new IncomingResponse(this._responseStream);
    response.once('ready', this.emit.bind(this, 'response', response));
  
    this.stream.on('promise', this._onPromise.bind(this));
  }
docs: IncomingPromise class -------------------------