code: function save(file, options) {
    var stream = fs.createWriteStream(file, options);
    function onSave() {
      stream.removeAllListeners();
      this.emit('save');
    }
    function onError(err) {
      stream.removeAllListeners();
      this.emit('error', err);
    }
    stream.on('finish', onSave.bind(this));
    stream.on('error', onError.bind(this));
    this.pipe(stream);
    return this;
  }
docs: Pipe the output of this writer to a file.