code: def _open_for_read(self):
          
          ownerid, datasetid = parse_dataset_key(self._dataset_key)
          response = requests.get(
              '{}/file_download/{}/{}/{}'.format(
                  self._query_host, ownerid, datasetid, self._file_name),
              headers={
                  'User-Agent': self._user_agent,
                  'Authorization': 'Bearer {}'.format(
                      self._config.auth_token)
              }, stream=True)
          try:
              response.raise_for_status()
          except Exception as e:
              raise RestApiError(cause=e)
          self._read_response = response
docs: open the file in read mode