docs: public java.util.Iterator iterator() {
          // TODO Bug in remove from a concurrentSet/Map iterator, it does not actually do the remove!
          java.util.Set combinedSet = new java.util.HashSet();
          if (subSets != null) {
              for (int i = 0; i < subSets.length; i++) {
                  synchronized (subSets[i]) {
                      combinedSet.addAll(subSets[i]);
                  } // synchronized (subSet).
              }
          }
          return combinedSet.iterator();
      }