What is app_flutter directory in dart/flutter

Question

I'm working on a flutter application, and I want to write to a JSON file.

My JSON file is in the 'assets/' folder that I created and added to pubspec.yaml. I can get the data using :

final String res2 = await rootBundle.loadString("assets/profile.json");

I went through here to get the path to the file: https://docs.flutter.dev/cookbook/persistence/reading-writing-files,

Like this :

Future<File> get _localFile async {
  final path = await _localPath;
  return File('$path/assets/profile.json');
}

Future<String> get _localPath async {
  final directory = await getApplicationDocumentsDirectory();
  return directory.path;
}

Future<File> writeJSON(newDatas) async {
  final file = await _localFile;
  // Write the file
  return file.writeAsString('$newDatas');
}

But when I try to access the file, I get this error:

Cannot open file, path = '/data/user/0/com.example.myapp/app_flutter/assets/profile.json'

Do you know why?

Thank you!