@NotNull
  @Override
  public List<IndentTransferableData> extractTransferableData(@NotNull Transferable content) {
    IndentTransferableData indentData = new IndentTransferableData(-1);
    try {
      final DataFlavor flavor = IndentTransferableData.getDataFlavorStatic();
      if (flavor != null) {
        final Object transferData = content.getTransferData(flavor);
        if (transferData instanceof IndentTransferableData) {
          indentData = (IndentTransferableData)transferData;
        }
      }
    }
    catch (UnsupportedFlavorException | IOException e) {
      // do nothing
    }
    return Collections.singletonList(indentData);
  }
@NotNull
  @Override
  public List<IndentTransferableData> extractTransferableData(@NotNull Transferable content)