code: func (g *UndirectedGraph) Nodes() []graph.Node {
  	nodes := make([]graph.Node, len(g.nodes))
  	i := 0
  	for _, n := range g.nodes {
  		nodes[i] = n
  		i++
  	}
  
  	return nodes
  }
docs: // Nodes returns all the nodes in the graph.