docs: async def _handle_future_salts(self, message):
          """
          Handles future salt results, which don't come inside a
          ``rpc_result`` but are still sent through a request:
  
              future_salts#ae500895 req_msg_id:long now:int
              salts:vector<future_salt> = FutureSalts;
          """
          # TODO save these salts and automatically adjust to the
          # correct one whenever the salt in use expires.
          self._log.debug('Handling future salts for message %d', message.msg_id)
          state = self._pending_state.pop(message.msg_id, None)
          if state:
              state.future.set_result(message.obj)