code: function(options) {
    stream.Duplex.call(this, { objectMode: true });
  
    this.options = extend(true, Pipeline.DEFAULTS, options || {});
    this.readyState = 0; // 0: closed, 1: open
  
    this._pipeline = [];
  
    this.setMaxListeners(0); // unlimited listeners allowed
  
    this.options.ipc.subscribe(
      this.options.ipc.namespace,
      this._proxy.bind(this)
    );
  }
docs: A stream of "activities" that flow through a handler pipeline.
  @constructor
  @param {object} options - a configuration object