code: async def slaveof(self, host=None, port=None):
          
          if host is None and port is None:
              return await self.execute_command('SLAVEOF', b('NO'), b('ONE'))
          return await self.execute_command('SLAVEOF', host, port)
docs: Set the server to be a replicated slave of the instance identified
          by the ``host`` and ``port``. If called without arguments, the
          instance is promoted to a master instead.