code: @Override
      protected long checksum() {
          Map<String, Object> attrs = getAttributes();
          if (attrs == null) {
              return 0;
          }
          if (dataJson != null) {
              attrs.put(ATTR_DATA, dataJson);
          }
          return HashUtils.checksum(attrs, HashUtils.murmur3);
      }
docs: {@inheritDoc}
  
  @since 0.10.0