code: function bidirectionalClickBinding (event) {
          var bind = this._bindingListeners.selectedValue;
          var newValue = this._transform(bind.transform, this._cfg.value, "fromWidget");
          ariaUtilsJson.setValue(bind.inside, bind.to, newValue);
      }
docs: Being a BindableWidget we already have one direction binding of checked (from the datamodel to the widget). This
  function is the callback for implementing the other bind, from the widget to the datamodel. The checked property
  is set in the datamodel on click.
  @param {aria.DomEvent} event click event
  @private