code: public Iterable<DUser> queryByPreferredLanguage(java.lang.String preferredLanguage) {
      return queryByField(null, DUserMapper.Field.PREFERREDLANGUAGE.getFieldName(), preferredLanguage);
    }
docs: query-by method for field preferredLanguage
  @param preferredLanguage the specified attribute
  @return an Iterable of DUsers for the specified preferredLanguage