public int compareTo(AnnotationArgument a) {
   int rc = role.compareTo(a.getRole());
   if (rc == 0) {
     return arg.compareTo(a.getArg());
   } else return rc;
 }
 public int compare(AnnotationArgument a1, AnnotationArgument a2) {
   SpanList a1Sp = a1.getArg().getSpan();
   SpanList a2Sp = a2.getArg().getSpan();
   if (SpanList.atLeft(a2Sp, a1Sp)) return 1;
   return -1;
 }