code: public long calcChecksum() {
          if (checksum == null) {
              Lock lock = lockForRead();
              try {
                  checksum = checksum();
              } finally {
                  lock.unlock();
              }
          }
          return checksum.longValue();
      }
docs: Calculate the checksum of BO's attributes (ignore "dirty" flag).
  
  @return
  @since 0.10.0