#NEWLINE# def get_product_variant( self , extra ) : #NEWLINE# #INDENT# '\n        Get a variant of the product or itself, if the product has no flavors.\n        Raises `Product.objects.DoesNotExists` if there is no variant for the given `extra`.\n        ' #NEWLINE# msg = 'Method get_product_variant(extra) must be implemented by subclass: `{}`' #NEWLINE# raise NotImplementedError ( msg . format ( extra . __class__ . __name__ ) )