private ThreadGroupIterator allThreadGroups() throws NoSessionException {
   threads = null;
   return new ThreadGroupIterator(runtime.topLevelThreadGroups());
 }
 private ThreadIterator allThreads() throws NoSessionException {
   threads = null;
   // ### Why not use runtime.allThreads().iterator() ?
   return new ThreadIterator(runtime.topLevelThreadGroups());
 }