public Map<String, String> getTypes(final Set<String> streamIds,
                                        final Set<String> fields) {
        final Map<String, Set<String>> allFieldTypes = this.get(streamIds);

        final Map<String, String> result = new HashMap<>(fields.size());
        fields.forEach(field -> {
            final Set<String> fieldTypes = allFieldTypes.get(field);
            typeFromFieldType(fieldTypes).ifPresent(s -> result.put(field, s));
        });

        return result;
    }
@Test
    void getTypesReturnsEmptyMapIfFieldTypesAreEmpty() {
        final Pair<IndexFieldTypesService, StreamService> services = mockServices();
        final FieldTypesLookup lookup = new FieldTypesLookup(services.getLeft(), services.getRight());
        assertThat(lookup.getTypes(Set.of("SomeStream"), Set.of("somefield"))).isEmpty();
    }