Realm access from incorrect thread Exception while a copy was sent using copyFromRealm

When streaming copy of realm objects instead of realm reference and observing it on Schedulers.IO thread, there is a crash with the famous exception message "Realm access from incorrect thread. Realm objects can only be accessed in the thread they were created."

Shouldn't the copy be thread free? Can I produce it from one thread and process it on a different thread?

This is how I am creating observable.

 public Observable<Brand> getAllBrands() {
    return realm.where(Brand.class)
            .findAll()
            .asObservable()
            .flatMap(Observable::from)
            .map(brand -> realm.copyFromRealm(brand));
}

Following is how I observe getAllBrands().

 Observable<Brand> brandObservable = dataManager.getAllBrands();

    brandObservable.observeOn(AndroidSchedulers.mainThread())
            .subscribeOn(Schedulers.io())
            .subscribe(new Observer<Brand>() {
                @Override
                public void onCompleted() {
                    Log.d("reactive", "completed");
                }

                @Override
                public void onError(Throwable e) {
                    Log.d("reactive", e.getMessage());
                }

                @Override
                public void onNext(Brand brand) {
                    dataSource.add(brand.getName());
                    myAdapter.notifyDataSetChanged();
                }
            });