if (parent == null) return null;
DefaultMutableTreeNode sibling = getPreviousSibling(); if (sibling != null) return sibling.getLastLeaf();  if (parent != null) return ((DefaultMutableTreeNode) parent).getPreviousLeaf();
  public DefaultMutableTreeNode getPreviousLeaf()  {    if (parent == null)      return null;        // TODO: Fix implementation.    return null;    //return parent.getChildBefore(this);  }