code: func (sn *SimNode) Stop() error {
  	sn.lock.Lock()
  	if sn.client != nil {
  		sn.client.Close()
  		sn.client = nil
  	}
  	sn.lock.Unlock()
  	return sn.node.Stop()
  }
docs: // Stop closes the RPC client and stops the underlying devp2p node