Using translate field for 'unique' rises NameError, django-parler

Question

I've recently installed django-parler==2.2 and when I rewrite my model to inherit from TranslatableModel and then try to makemigrations I get the following error:

main_menu_slug = models.SlugField(max_length=120, unique=main_menu_item) NameError: name 'main_menu_item' is not defined

Everything runs fine when I inherit from models.Model. Here is the code:

class MenuItem(TranslatableModel):

    translations = TranslatedFields (
        main_menu_item = models.CharField(max_length=60),
        main_menu_slug = models.SlugField(max_length=120, unique=main_menu_item)
    )

I've just started using this module, so possibly it is something trivial but I couldn't find the solution. What I am doing wrong?

Full Traceback:

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    main()
  File "manage.py", line 18, in main
    execute_from_command_line(sys.argv)
  File "C:\project\alfa\lib\site-packages\django\core\management\__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "C:\project\alfa\lib\site-packages\django\core\management\__init__.py", line 377, in execute
    django.setup()
  File "C:\project\alfa\lib\site-packages\django\__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "C:\project\alfa\lib\site-packages\django\apps\registry.py", line 114, in populate
    app_config.import_models()
  File "C:\project\alfa\lib\site-packages\django\apps\config.py", line 211, in import_models
    self.models_module = import_module(models_module_name)
  File "C:\Users\user\AppData\Local\Programs\Python\Python37\lib\importlib\__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "C:\project\alfa\project\menus\models.py", line 16, in <module>
    class MenuItem(TranslatableModel):
  File "C:\project\alfa\project\menus\models.py", line 20, in MenuItem
    main_menu_slug = models.SlugField(max_length=120, unique=main_menu_item)
NameError: name 'main_menu_item' is not defined

Working code models.Model:

class MenuItem(models.Model):
    main_menu_item = models.CharField(max_length=60)
    main_menu_slug = models.SlugField(max_length=120, unique=main_menu_item)

Answer 1

unique should be a boolean value as per the docs: https://docs.djangoproject.com/en/3.1/ref/models/fields/#unique