public SortedMap get(int start, int end, Object label) { return (SortedMap)chart[start][end].get(label);
public Iterator get(int start, int end) { return chart[start][end].map.keySet().iterator();
  public SortedMap get(int start, int end, Object label) {    return (SortedMap)chart[start][end].get(label);  }