async showAt(opener) {
      if ((0, _Device.isPhone)()) {
        this._prepareCurrentItems(this.items);
        this._parentItemsStack = [];
      }
      if (!this._isSubMenu) {
        this._parentMenuItem = undefined;
      }
      const popover = await this._createPopover();
      popover.initialFocus = "";
      for (let index = 0; index < this._currentItems.length; index++) {
        if (!this._currentItems[index].item.disabled) {
          popover.initialFocus = `${this._id}-menu-item-${index}`;
          break;
        }
      }
      popover.showAt(opener);
    }
Shows the Menu near the opener element.
@param {HTMLElement} opener the element that the popover is shown at
@public
@method
@name sap.ui.webc.main.Menu#showAt