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() throws Exception {
        List<Actor> actors = Arrays.asList(new Actor("Keanu Reeves"), new Actor("Laurence Fishburne"), new Actor("Carrie-Anne Moss"));
        MovieActorReference movieSetReference = new MovieActorReference(1, 1999, "The Matrix", actors);
        objectMapper.add(movieSetReference);
        StateEngineRoundTripper.roundTripSnapshot(writeStateEngine, readStateEngine);
        HollowPrefixIndex prefixIndex = new HollowPrefixIndex(readStateEngine, "MovieActorReference", "actors.element");
        Set<Integer> ordinals = toSet(prefixIndex.findKeysWithPrefix("kea"));
        Assert.assertTrue(ordinals.size() == 1);
    }