@Override
    public @Nullable ListSeparator getSeparatorAbove(T value) {
      final ListCellRenderer<? super T> cellRenderer = myGetRenderer.get();
      if (cellRenderer instanceof GroupedComboBoxRenderer<? super T> renderer) {
        return renderer.separatorFor(value);
      }
      if (cellRenderer instanceof ComboBoxWithWidePopup<? super T>.AdjustingListCellRenderer renderer
          && renderer.delegate instanceof GroupedComboBoxRenderer<? super T> delegate) {
        return delegate.separatorFor(value);
      }
      return null;
    }
@Override
    public @Nullable ListSeparator getSeparatorAbove(T value)