         return nil
     }
     
+    func onAllNodes(_ closure: (Node) -> Void) {
+        for node in nodeDict.values {
+            closure(node)
+        }
+    }
     
     public func update(_ aNode: Node) {
         // No implementation required for XMLFileStore

        // No implementation required for XMLFileStore
    }
    

    
    //MARK: - Relationship
    
    var relationshipList = [Relationship]()
    var maxRelationshipUID : UID = 0
    
    // Register a new or loaded relationship
    public func register(_ rel: Relationship) {

        //readXMLFile()
    }
    
    //MARK: - Graphs
    
    var graphList = [Graph]()
    
    public func register(_ graph: Graph) {
        graphList.append(graph)
    }

    //MARK: - Node
    
    //var nodeList = [Node]()
