anchor.diff:  const profilePeriod = 'profile_period';
   
   class VmFlagManager extends Disposer {
  -  VmServiceWrapper get service => _service;
  -  VmServiceWrapper _service;
  +  VmServiceWrapper? get service => _service;
  +  VmServiceWrapper? _service;
   
     ValueListenable get flags => _flags;
  -  final _flags = ValueNotifier<FlagList>(null);
  +  final _flags = ValueNotifier<FlagList?>(null);
   
  -  final _flagNotifiers = <String, ValueNotifier<Flag>>{};
  +  final _flagNotifiers = <String?, ValueNotifier<Flag>>{};
   
  -  ValueNotifier<Flag> flag(String name) {
  +  ValueNotifier<Flag>? flag(String name) {
       return _flagNotifiers.containsKey(name) ? _flagNotifiers[name] : null;
     }
   
     Future<void> _initFlags() async {
  -    final flagList = await service.getFlagList();
  +    final flagList = await service!.getFlagList() ?? FlagList(flags: []);
       _flags.value = flagList;
  -    if (flagList == null) return;
   
  -    for (var flag in flagList.flags) {
  +    for (var flag in flagList.flags ?? <Flag>[]) {
         _flagNotifiers[flag.name] = ValueNotifier<Flag>(flag);
       }
     }
  
positive.code:   void handleVmEvent(Event event) async {
      if (event.kind == EventKind.kVMFlagUpdate) {
        if (_flagNotifiers.containsKey(event.flag)) {
          final currentFlag = _flagNotifiers[event.flag].value;
          _flagNotifiers[event.flag].value = Flag.parse({
            'name': currentFlag.name,
            'comment': currentFlag.comment,
            'modified': true,
            'valueAsString': event.newValue,
          });
          _flags.value = await service.getFlagList();
        }
      }
    }
  
negative.code: // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  // ignore_for_file: import_of_legacy_library_into_null_safe
  
  import 'dart:core';
  
  