public HollowOrdinalIterator findKeysWithPrefix(String prefix) {
        TST current;
        HollowOrdinalIterator it;
        do {
            current = prefixIndexVolatile;
            it = current.findKeysWithPrefix(prefix);
        } while (current != this.prefixIndexVolatile);
        return it;
    }
@Test
    public void testMovieActorReference_duplicatesInList() throws Exception {
        List<Actor> actors = Collections.singletonList(new Actor("Keanu Reeves"));
        int numMovies = 10;
        IntStream.range(0, numMovies).mapToObj(index ->
                new MovieActorReference(index, 1999 + index, "The Matrix " + index, actors))
            .forEach(objectMapper::add);
        StateEngineRoundTripper.roundTripSnapshot(writeStateEngine, readStateEngine);
        HollowPrefixIndex prefixIndex = new HollowPrefixIndex(readStateEngine, "MovieActorReference", "actors.element");
        Assert.assertEquals(numMovies, toSet(prefixIndex.findKeysWithPrefix("kea")).size());
    }