public Searcher searcher() {
        return new Searcher();
    }
@Test
    void requireThatSearchesCanUseSubqueries() {
        PredicateIndexBuilder builder = new PredicateIndexBuilder(10);
        builder.indexDocument(DOC_ID, Predicate.fromString("country in [no] and gender in [male]"));
        PredicateIndex index = builder.build();
        PredicateIndex.Searcher searcher = index.searcher();

        PredicateQuery query = new PredicateQuery();
        query.addFeature("country", "no", 0x3);
        assertEquals(0, searcher.search(query).count());
        query.addFeature("gender", "male", 0x6);
        assertEquals("[[42,0x2]]", searcher.search(query).toList().toString());
    }