public static String inSeed(ITree t) {
   return ITree.OPEN_SYMBOL + t.getLabel() + ITree.SEPARATE_SYMBOL + t.getType();
 }
 public static String outSeed(ITree t) {
   return t.getType() + ITree.SEPARATE_SYMBOL + t.getLabel() + ITree.CLOSE_SYMBOL;
 }
 public static int standardHash(ITree t) {
   return Integer.hashCode(t.getType()) + HashUtils.BASE * t.getLabel().hashCode();
 }