code: def notify_client(
          notifier_uri,
          client_id,
          status_code,
          message=None):
      
      payload = {
          "client_id": client_id,
          "result": {
              "response": {
                  "status_code": status_code
              }
          }
      }
  
      if message is not None:
          payload["result"]["response"]["message"] = message
  
      response = requests.post(notifier_uri, json=payload)
  
      if response.status_code != 201:
          sys.stderr.write("failed to notify client: {}\n".format(payload))
          sys.stderr.flush()
docs: Notify the client of the result of handling a request
  
      The payload contains two elements:
  
      - client_id
      - result
  
      The *client_id* is the id of the client to notify. It is assumed
      that the notifier service is able to identify the client by this id
      and that it can pass the *result* to it.
  
      The *result* always contains a *status_code* element. In case the
      message passed in is not None, it will also contain a *message*
      element.
  
      In case the notifier service does not exist or returns an error,
      an error message will be logged to *stderr*.