code: private static Map<Elements, String> casIds() {
          Map<Elements, String> result = ids;
          if (result == null) {
              synchronized (LOCK) {
                  result = ids;
                  if (result == null) {
                      ids = result = initCasIds();
                  }
              }
          }
          return result;
      }
docs: Lazily obtain the CAS ID Mapping.
  
  @return CAS id mapping