code: function (event) {
      if (!event || !_.isObject(event)) {
        var err = new Error('Please inject a valid event object!');
        debug(err);
        throw err;
      }
  
      if (!event.payload && event.payload !== '') {
        event.payload = this.defaultEventPayload;
      }
  
      if (this.events.indexOf(event) < 0) {
        this.events.push(event);
      }
    }
docs: Add event module.
  @param {Event} event The event module to be injected.