anchor.diff:        result['externals'] = externalsToAnalyze;
       } else if (library.isFiltered) {
         final filtersToAnalyze = <ClassReference>[];
  -      for (final LibraryReference libraryRef in library.children) {
  -        for (final ClassReference classRef in libraryRef.children) {
  -          final HeapGraphClassLive liveClass = classRef.actualClass;
  +      for (final LibraryReference libraryRef
  +          in library.children as Iterable<LibraryReference>) {
  +        for (final ClassReference classRef
  +            in libraryRef.children as Iterable<ClassReference>) {
  +          final HeapGraphClassLive liveClass = classRef.actualClass!;
             if (_classMatcher(liveClass)) {
               filtersToAnalyze.add(classRef);
               final instances = liveClass.getInstances(heapGraph);
  
positive.code: ClassFields fieldsStack = ClassFields();
  
  Map<String, List<String>> drillIn(
    MemoryController controller,
    AnalysisReference librariesNode,
    List<Reference> references, {
    createTreeNodes = false,
  
negative.code: final _debugMonitorClasses = ['ImageCache'];
  
  /// Class being monitored if its name is in the debugMonitorClasses.
  String? _debugMonitorClass;
  
  void _debugMonitor(String msg) {
    if (!_debugMonitorEnabled || _debugMonitorClass == null) return;
  