code: def _get_success(self, stanza):
          
          payload = stanza.get_payload(RosterPayload)
          if payload is None:
              if "versioning" in self.server_features and self.roster:
                  logger.debug("Server will send roster delta in pushes")
              else:
                  logger.warning("Bad roster response (no payload)")
                  self._event_queue.put(RosterNotReceivedEvent(self, stanza))
                  return
          else:
              items = list(payload)
              for item in items:
                  item.verify_roster_result(True)
              self.roster = Roster(items, payload.version)
          self._event_queue.put(RosterReceivedEvent(self, self.roster))
docs: Handle successful response to the roster request.