docs: function (element, opacity) {
              var browser = ariaCoreBrowser;
              var isIE8OrLess = (browser.isIE8 || browser.isIE7);
              this.setOpacity = isIE8OrLess ? this._setOpacityLegacyIE : this._setOpacityW3C;
              this.setOpacity(element, opacity);
          }