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