code: def remove_client(self, client_identifier):
          
          new_clients = self.clients
          new_clients.remove(client_identifier)
          yield from self._server.group_clients(self.identifier, new_clients)
          _LOGGER.info('removed %s from %s', client_identifier, self.identifier)
          self._server.client(client_identifier).callback()
          self.callback()
docs: Remove a client.