docs: function (viewBuilder) {
      if (!viewBuilder || !_.isObject(viewBuilder)) {
        var err = new Error('Please inject a valid view builder object!');
        debug(err);
        throw err;
      }
      if (viewBuilder.payload === null || viewBuilder.payload === undefined) {
        viewBuilder.payload = this.defaultPayload;
      }
      if (this.viewBuilders.indexOf(viewBuilder) < 0) {
        viewBuilder.useCollection(this);
        this.viewBuilders.push(viewBuilder);
      }
    }