code: def download_data_impl(self, run, tag, response_format):
      
      scalars_plugin_instance = self._get_scalars_plugin()
      if not scalars_plugin_instance:
        raise ValueError(('Failed to respond to request for /download_data. '
                          'The scalars plugin is oddly not registered.'))
  
      body, mime_type = scalars_plugin_instance.scalars_impl(
          tag, run, None, response_format)
      return body, mime_type
docs: Provides a response for downloading scalars data for a data series.
  
      Args:
        run: The run.
        tag: The specific tag.
        response_format: A string. One of the values of the OutputFormat enum of
          the scalar plugin.
  
      Raises:
        ValueError: If the scalars plugin is not registered.
  
      Returns:
        2 entities:
          - A JSON object response body.
          - A mime type (string) for the response.