public ClosableIterator<Long[]> iterator() {
ClosableIterator<Map.Entry<Long, ClosableMap<Long, ClosableMap<Long, ClosableMap<Long, Set<Long>>>>>> iterator =
new ClosableIteratorImpl<Map.Entry<Long, ClosableMap<Long, ClosableMap<Long, ClosableMap<Long,
Set<Long>>>>>>(index.entrySet().iterator());
return new FlatteningFiveLongClosableIterator(iterator);
}