code: def send_request(self, request):
          
          if request.observe == 0:
              # Observe request
              host, port = request.destination
              key_token = hash(str(host) + str(port) + str(request.token))
  
              self._relations[key_token] = ObserveItem(time.time(), None, True, None)
  
          return request
docs: Add itself to the observing list
  
          :param request: the request
          :return: the request unmodified