text: def main(request, response):
      headers = [(b"Content-Type", b"text/javascript")]
  
      values = []
      for key in request.cookies:
          for cookie in request.cookies.get_list(key):
              values.append(b'"%s": "%s"' % (key, cookie.value))
  
      # Update the counter to change the script body for every request to trigger
      # update of the service worker.
      key = request.GET[b'key']
      counter = request.server.stash.take(key)
      if counter is None:
          counter = 0
      counter += 1
      request.server.stash.put(key, counter)
  
      body = b"""
  // %d
  self.addEventListener('message', e => {
    e.source.postMessage({%s})
  });""" % (counter, b','.join(values))
  
      return headers, body
  