code: function(log) {
    var date = this.date.toISOString().substring(0, 19);
    var duration = new Date() - this.date;
    log(date + ' ' + this.ip + ' "' + this.method + ' ' + this.path + '" ' + this.status + ' ' + this._length + ' ' + duration);
  }
docs: Log response.
  
  @param {function} log