code: func VertexName(raw Vertex) string {
  	switch v := raw.(type) {
  	case NamedVertex:
  		return v.Name()
  	case fmt.Stringer:
  		return fmt.Sprintf("%s", v)
  	default:
  		return fmt.Sprintf("%v", v)
  	}
  }
docs: // VertexName returns the name of a vertex.