class MapValue implements Comparable<MapValue<V>> {

    public static <U> MapValue<U> tombstone(Timestamp timestamp) {
        return new MapValue<>(null, timestamp, System.currentTimeMillis());
    }

    public  MapValue(V value, Timestamp timestamp);
    public  MapValue(V value, Timestamp timestamp, long creationTime);
    @SuppressWarnings("unused") private  MapValue();

}