toJson method Null safety

Implementation

@override
Map<String, dynamic> toJson() {
  final json = <String, dynamic>{};
  json['type'] = type;
  json.addAll({
    'name': name,
    'architectureBits': architectureBits,
    'hostCPU': hostCPU,
    'operatingSystem': operatingSystem,
    'targetCPU': targetCPU,
    'version': version,
    'pid': pid,
    'startTime': startTime,
    'isolates': isolates?.map((f) => f.toJson()).toList(),
    'isolateGroups': isolateGroups?.map((f) => f.toJson()).toList(),
    'systemIsolates': systemIsolates?.map((f) => f.toJson()).toList(),
    'systemIsolateGroups':
        systemIsolateGroups?.map((f) => f.toJson()).toList(),
  });
  return json;
}