class Person {
    List<Address> addresses;
}

public interface PersonRepository extends ReactiveMongoRepository<Person, String>{
}

Flux<Addresses> getAddressesByPersonId(String personId)

public Flux<Addresses> getAddressesByPersonId(String personId){
    Mono<Person> person = personRepository.findById(personId);
    return person.map(e -> e.getAdresses()).flux()
}

Type mismatch: cannot convert from Flux<List<Person>> to Flux<Person>