code: function (zIndex, modalMaskZIndex) {
              var computedStyle = this.computedStyle;
              if (computedStyle) {
                  computedStyle.zIndex = zIndex;
                  if (modalMaskZIndex != null) {
                      this.modalMaskZIndex = modalMaskZIndex;
                  }
                  this.refresh();
              }
          }
docs: Sets the zIndex of the popup, and refreshes. The zIndex of the modal mask, if any, is not changed,
  unless the second parameter is defined.
  This method does nothing if the popup has not already been displayed.
  @param {Number} zIndex zIndex to set on the popup.
  @param {Number} modalMaskZIndex zIndex to set on the modal mask.