@Override
 public void visitLineNumber(final int line, final Label start) {
   // Here we rely on the usage of the info fields by the tree API. If the
   // labels have been properly used before the info field contains a
   // reference to the LabelNode, otherwise null.
   if (start.info != null) {
     super.visitLineNumber(line, start);
   }
 }
 @Override
 public void visitLocalVariable(
     final String name,
     final String desc,
     final String signature,
     final Label start,
     final Label end,
     final int index) {
   // Here we rely on the usage of the info fields by the tree API. If the
   // labels have been properly used before the info field contains a
   // reference to the LabelNode, otherwise null.
   if (start.info != null && end.info != null) {
     super.visitLocalVariable(name, desc, signature, start, end, index);
   }
 }