if !exists {
		namespacedVertices = map[string]*namedVertex{}
		typedVertices[namespace] = namespacedVertices
	}

	vertex := newNamedVertex(vertexType, namespace, name, g.graph.NewNodeID())
	namespacedVertices[name] = vertex
	g.graph.AddNode(vertex)

	return vertex
}

// must be called under write lock
func (g *Graph) deleteVertex_locked(vertexType vertexType, namespace, name string) {