// nameVertexMapping is a map of name -> vertex
type nameVertexMapping map[string]*namedVertex

func NewGraph() *Graph {
	return &Graph{
		vertices: map[vertexType]namespaceVertexMapping{},
		graph:    simple.NewDirectedAcyclicGraph(0, 0),

		destinationEdgeIndex: map[int]*intSet{},
		// experimentally determined to be the point at which iteration adds an order of magnitude to the authz check.