code: async def on_raw_410(self, message):
          
          self.logger.error('Server sent "Unknown CAP subcommand: %s". Aborting capability negotiation.', message.params[0])
  
          self._capabilities_requested = set()
          self._capabilities_negotiating = set()
          await self.rawmsg('CAP', 'END')
docs: Unknown CAP subcommand or CAP error. Force-end negotiations.