docs: function sort(children, sortOrder) {
      if (typeof sortOrder === 'function') {
          return children.sort(sortOrder);
      }
      else {
          var isAsc = sortOrder === 'asc';
          return children.sort(function (a, b) {
              var diff = (a.getValue() - b.getValue()) * (isAsc ? 1 : -1);
              return diff === 0
                  ? (a.dataIndex - b.dataIndex) * (isAsc ? -1 : 1)
                  : diff;
          });
      }
  }