return null;
throw new IllegalArgumentException("Not a DefaultMutableTreeNode or DMTNArray");
  public Transferable makeDraggableObject(Object o) {    if (o instanceof DefaultMutableTreeNode) {      return new ConsoleTreeObjectTransferable((DefaultMutableTreeNode) o);    } else if (o instanceof DMTNArray) {      return new CTOArrayTransferable((DMTNArray) o);    }    return null;  }