@Override
        public Tuple<T> next() {
            KV<String, T> next = it.next();
            if (next == null)
                return null;
            else
                return new Tuple<>(next.getKey(), next.getValue());
        }
DEPRECATED: may cause OutOfMemoryError on large crawls.

@return
ache/src/main/java/achecrawler/util/persistence/PersistentHashtable.java