code: def _serve_audio_metadata(self, request):
      
      tag = request.args.get('tag')
      run = request.args.get('run')
      sample = int(request.args.get('sample', 0))
  
      events = self._multiplexer.Tensors(run, tag)
      response = self._audio_response_for_run(events, run, tag, sample)
      return http_util.Respond(request, response, 'application/json')
docs: Given a tag and list of runs, serve a list of metadata for audio.
  
      Note that the actual audio data are not sent; instead, we respond
      with URLs to the audio. The frontend should treat these URLs as
      opaque and should not try to parse information about them or
      generate them itself, as the format may change.
  
      Args:
        request: A werkzeug.wrappers.Request object.
  
      Returns:
        A werkzeug.Response application.