code: static DatastoreException translateAndThrow(RetryHelperException ex) {
      BaseServiceException.translate(ex);
      throw new DatastoreException(UNKNOWN_CODE, ex.getMessage(), null, ex.getCause());
    }
docs: Translate RetryHelperException to the DatastoreException that caused the error. This method
  will always throw an exception.
  
  @throws DatastoreException when {@code ex} was caused by a {@code DatastoreException}