private static void testTransAndUntrans(
     CharacterLevelTagExtender e, Treebank tb, PrintWriter pw) {
   for (Tree tree : tb) {
     Tree oldTree = tree.treeSkeletonCopy();
     e.transformTree(tree);
     CharacterLevelTagExtender.untransformTree(tree);
     if (!tree.equals(oldTree)) {
       pw.println("NOT EQUAL AFTER UNTRANSFORMATION!!!");
       pw.println();
       oldTree.pennPrint(pw);
       pw.println();
       tree.pennPrint(pw);
       pw.println("------------------");
     }
   }
 }