docs: function (newValue) {
              if (newValue == null) {
                  // a null value is allowed for the selectedIndex property, but it cannot be used to set the property
                  // as it means several items are selected and we do not know which ones
                  // just ignore the null value
                  return;
              }
              var items = this._data.items;
              if (newValue < 0 || newValue >= items.length) {
                  // unselect all values in case newValue is -1 or invalid
                  this.setSelectedValues([]);
              } else {
                  this.setSelectedValues([items[newValue].value]);
              }
          }