static void deleteConcept(long id) {
  db_mainConcepts().deleteConcept(id);
}

static void deleteConcept(Concepts concepts, long id) {
  concepts.deleteConcept(id);
}

static void deleteConcept(Concept c) {
  if (c != null) c.delete();
}

static void deleteConcept(Concept.Ref ref) {
  if (ref != null) deleteConcept(ref.get());
}