def process_object(self, obj):
return obj<EOL>
Process an object before it will be used to create a cart item.

        This method provides a hook to perform arbitrary actions on
        the item's model instance, before it gets associated with the
        cart item. However, it's usually used just to replace the
        passed model instance with its related object. The default
        implementation simply returns the passed object.

        Parameters
        ----------
        obj : item model
            An item's model instance.

        Returns
        -------
        item model
            A model instance that will be used as the `obj` argument to
            :attr:`item_class`.