private IterableChecker<List<String>, String> ids(LongHolderCriteria criteria) {
    return CriteriaChecker.<TypeHolder.LongHolder>ofReader(repository.find(criteria)).toList(TypeHolder.LongHolder::id);
  }
Projection on a list type (eg. {@code List<Long>})
criteria/common/test/org/immutables/criteria/typemodel/LongTemplate.java