@RealmModel()
class _TodoModel {
@PrimaryKey()
@MapTo('_id')
late ObjectId id;
late String title;
late String description;
late String userId;
late List<$Notes> notes;
late Map<String, RealmValue> metaData;
}

 final metaData = RealmMap(
  {  
       'title' :  RealmValue.from("title string"),
       'description' : RealmValue.from("description)'
  };
);

final newTodo =
    TodoModel(
      ObjectId(), 
      todo.title, 
      todo.description,
      todo.userId,
        metaData: metaData
);

RealmConfig.instance.realm.write(() {
  RealmConfig.instance.realm.add(newTodo);
});

  final mapData = {
  "title" : 'xyz',
  "age",: 12,
  "dob" : DateTime.now(),
  'metaData' : {
     "a": 'a',
     "b" : 'b'
   }
}