code: function (context) {
                  var that = context;
                  assert(!!that, "No ToolPopup instance given for _fnGetInitialFocus");
  
                  // if there is an initial focus it was already set to the Popup onBeforeRendering
                  if (!that._bFocusSet) {
                      _fnGetNewFocusElement(that);
                  } else {
                      that._sInitialFocusId = that.oPopup._sInitialFocusId;
                  }
  
                  return that._sInitialFocusId;
              }
docs: Checks if the ToolPopup already has a tabbable element.
  If not, it's checked whether the fake-element should be used or if there is an element that could be focused instead.
  
  @param {sap.ui.ux3.ToolPopup} context to get/set instance values
  @returns {string} _sInitialFocusId that has been determined here
  @private