pfDao.getConcept(PfConceptKey.class, nullKey);
pfDao.getConcept(null, nullRefKey);
pfDao.getConcept(PfReferenceKey.class, nullRefKey);
pfDao.getConcept(PfConceptKey.class, nullKey);
pfDao.getConcept(null, nullRefKey);
pfDao.getConcept(PfReferenceKey.class, nullRefKey);