code: def get_existing_item(self, item):
          
          params = {
              'project_id': item.project_id,
              'from_user_id': item.from_user_id,
              'to_user_id': item.to_user_id,
          }
          resp = requests.get(self.make_url(item.destination), headers=self.json_headers, params=params)
          self.check_response(resp)
          return resp
docs: Lookup item in remote service based on keys.
          :param item: D4S2Item data contains keys we will use for lookup.
          :return: requests.Response containing the successful result