code: func (n *Node) Attr(name string) (starlark.Value, error) {
  	switch name {
  	case "key":
  		return n.Key, nil
  	case "props":
  		return n.Props, nil
  	case "trace":
  		return n.Trace, nil
  	default:
  		return nil, nil
  	}
  }
docs: // Attr is a part of starlark.HasAttrs interface.