public String graph() {
public String graph() throws Exception {
  public String graph() {    try {      StringBuffer resultBuff = new StringBuffer();      m_Tree.toGraph(resultBuff, 0);      String result = "digraph Tree {\n" + "edge [style=bold]\n" + resultBuff.toString()	+ "\n}\n";      return result;    } catch (Exception e) {      return null;    }  }