code: function (options) {
              var key;
              for (key in this.config) {
                  if (this.config.hasOwnProperty(key) && this.config[key].singleton) {
                      this._init(key, options);
                  }
              }
              return this;
          }
docs: Instantiate all singletons defined in the
  config.
  @param  {object} options Additional options
  @return {SubViewManager}