The clean repository from django application

gistfile1.txt

#mixin for repository
class RepositoryMixin():
    """ This class will served for base for all repository of project """
    class Meta:
        model = None

    @classmethod
    def all(cls):
        """
        Shortcut for get all entity from model
        return: QuerySet<Model>
        """
        return cls.Meta.model.objects.all()
    
    @classmethod
    def get(cls,**kwargs):
        """
        Shortcut for get method of model
        return: Model
        """
        return cls.Meta.model.objects.get(**kwargs)

    @classmethod
    def filter(cls, **kwargs):
        """
        Shortcut for filter method of model
        return: QuerySet<Model>
        """
        return cls.Meta.model.objects.filter(**kwargs)
    
    @classmethod
    def create(cls,**kwargs):
        """
        Shortcut for create method of model
        return: Model
        """
        return cls.Meta.model.objects.create(**kwargs)
        
#repository
# the logic of business 
# exemple of buy one product
class ProductRepository(RepositoryMixin):
    class Meta:
        model = Product
    
    @classmethod
    def buy_product(cls,pk):
        product = cls.get(pk=pk)
        #have in stock
        if product.amount > 0:
            product.amount -= 1
            product.save()
            return 'Sold :)'
        else:
            raise Exception('Out of stock :(')