code: def add_payload(self, key, val, append=True):
          
          if append:
              self._params.setdefault(key, []).append(val)
          else:
              self._params[key] = val
docs: Add a key value pair to payload for this request.
  
          .. Note:: For ``_search`` you can pass a search argument. (e.g. _search?summary=1.1.1.1).
  
          Args:
              key (string): The payload key
              val (string): The payload value
              append (bool): Indicates whether the value should be appended or overwritten.