maxGraph
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
@@ -139,6 +139,7 @@ export * as mathUtils from './util/mathUtils';
 export * as printUtils from './util/printUtils';
 export * as stringUtils from './util/StringUtils';
 export * as styleUtils from './util/styleUtils';
+export * as treeTraversalUtils from './util/treeTraversal';
 export * as utils from './util/Utils';
 export * as xmlUtils from './util/xmlUtils';
 

diff --git a/packages/core/src/util/treeTraversal.ts b/packages/core/src/util/treeTraversal.ts
@@ -115,6 +115,8 @@ export function findTreeRoots(
  * @param inverse Optional boolean to traverse in inverse direction. Default is false.
  * This is ignored if directed is false.
  */
+// TODO move from mxGraph class --> document in migration guide
+// check if we change the signature of the function by using an object as parameter as in graphlayout
 export function traverse(
   vertex: Cell | null = null,
   directed = true,
@@ -123,7 +125,9 @@ export function traverse(
   visited: Dictionary<Cell, boolean> | null = null,
   inverse = false
 ) {
+  // TODO simplify: exit right away if the 2 parameters are null
   if (func != null && vertex != null) {
+    // TODO remove the default values management here as this can be done in the signature (visited = new Dictionary<Cell, boolean>())
     directed = directed != null ? directed : true;
     inverse = inverse != null ? inverse : false;
     visited = visited || new Dictionary<Cell, boolean>();

diff --git a/packages/core/src/view/Graph.ts b/packages/core/src/view/Graph.ts
@@ -637,6 +637,12 @@ class Graph extends EventSource {
       const newParent = change.child.getParent();
       this.view.invalidate(change.child, true, true);
 
+      // TODO verify if change is needed
+      // from PR 88 fix, 1st element in if was "newParent &&"
+      //      if (newParent == null || !this.getDataModel().contains(newParent) || newParent.isCollapsed())
+      // original mxGraph
+      // 		if (!this.model.contains(newParent) || this.isCellCollapsed(newParent))
+      // condition changed in #115
       if (
         !newParent ||
         !this.getDataModel().contains(newParent) ||