code: def stop(self) -> None:
          
          if self._stopped:
              return
          self._stopped = True
          for fd, sock in self._sockets.items():
              assert sock.fileno() == fd
              # Unregister socket from IOLoop
              self._handlers.pop(fd)()
              sock.close()
docs: Stops listening for new connections.
  
          Requests currently in progress may still continue after the
          server is stopped.