docs: public void valueIterated(Object key) {
        // If we set to null that tells segment completion to just notify above in accept
        if (!currentKey.compareAndSet(key, null)) {
           // Otherwise we have to check if this key was linked to a group of pending segments
           Supplier<PrimitiveIterator.OfInt> segments = pendingSegments.remove(key);
           if (segments != null) {
              completionListener.accept(segments);
           }
        }
     }