class CatalogItem:
    """
    Decorator class, collect all catalog modules and his item classes in cls.REGISTRY
    """

    REGISTRY = {}

    def __init__(self, name):
        self.verbose_name = name

    def __call__(self, cls):
        self.register(cls)
        return cls

    def register(self, cls):
        """
        Register item modules and its item classes.
        :param cls: Class object
        :return:
        """
        module_name, module = self.register_module(cls)
        self.__class__.REGISTRY[module_name] = self.register_item(module, cls)

@CatalogItem('Куплю квартиру')
class FlatBuy(BaseAd):
    building_type = BuildingTypeField(choices=BuildingTypeField.get_choices_for_model_field())