@Override
  public void redo() throws CannotUndoException {
    super.redo();

    new DeleteColumnC(deletedVariables);
    unselectAll();
  }
 @Override
 public void undo() throws CannotRedoException {
   super.undo();
   for (Variable var : deletedVariables) {
     model.addVariable(var);
   }
 }