g.Nodes = append(g.Nodes, label)
	g.edges[label] = map[string]bool{}
	return true
}

func (g *Graph) AddEdge(from, to string) {
	g.edges[from][to] = true
}

func (g *Graph) DelEdge(from, to string) {
	delete(g.edges[from], to)
}

func (g *Graph) HasEdge(from, to string) bool {
	return g.edges[from] != nil && g.edges[from][to]
}

func (g *Graph) Edges(from string) []string {