code: function _quitAltGrMode() {
          _enabled = true;
          _ctrlDown = CtrlDownStates.NOT_YET_DETECTED;
          _altGrDown = false;
          _lastTimeStamp = null;
          _lastKeyIdentifier = null;
          $(window).off("keyup", _onCtrlUp);
      }
docs: @private
  Resets all the flags and removes _onCtrlUp event listener.