code: func (n *Node) RPCHandler() (*rpc.Server, error) {
  	n.lock.RLock()
  	defer n.lock.RUnlock()
  
  	if n.inprocHandler == nil {
  		return nil, ErrNodeStopped
  	}
  	return n.inprocHandler, nil
  }
docs: // RPCHandler returns the in-process RPC request handler.