onWriteFile method
Implementation
@override
Future<void> onWriteFile(String path, Stream<List<int>> byteStream) async {
  IOSink sink = toFile(path).openWrite();
  await sink.addStream(byteStream);
  await sink.flush();
  await sink.close();
}@override
Future<void> onWriteFile(String path, Stream<List<int>> byteStream) async {
  IOSink sink = toFile(path).openWrite();
  await sink.addStream(byteStream);
  await sink.flush();
  await sink.close();
}