code: private NlsRuntimeException unwrapNlsUserError(Throwable exception) {
  
      Throwable cause = exception.getCause();
      if (cause instanceof NlsRuntimeException) {
        NlsRuntimeException nlsError = (NlsRuntimeException) cause;
        if (nlsError.isForUser()) {
          return nlsError;
        }
      }
      return null;
    }
docs: Unwraps potential NLS user error from a wrapper exception such as {@code JsonMappingException} or
  {@code PersistenceException}.
  
  @param exception the exception to unwrap.
  @return the unwrapped {@link NlsRuntimeException} exception or {@code null} if no
  {@link NlsRuntimeException#isForUser() use error}.