code: def _validate_namespace(self, namespace):
          
          if self._namespace_regex.fullmatch(namespace) is None:
              LOGGER.debug('Invalid namespace: %s', namespace)
              raise _ResponseFailed(self._status.INVALID_ADDRESS)
docs: Validates a namespace, raising a ResponseFailed error if invalid.
  
          Args:
              state_root (str): The state_root to validate
  
          Raises:
              ResponseFailed: The state_root was invalid, and a status of
                  INVALID_ROOT will be sent with the response.