public void remove() {
      Node<K> p;
      if ((p = lastReturned) == null) {
        throw new IllegalStateException();
      }
      lastReturned = null;
      set.removeNode(p.key);
    }
Base of key, value, and entry Iterators. Adds fields to Traverser to support iterator.remove.
geode-core/src/main/java/org/apache/geode/internal/concurrent/CompactConcurrentHashSet2.java