CartClear. Removes all items from cart
        :param CartId: Id of cart
        :param HMAC: HMAC of cart. Do not use url encoded
        :return: An :class:`~.AmazonCart`.

def cart_clear(self, CartId=None, HMAC=None, **kwargs):
        """CartClear. Removes all items from cart
        :param CartId: Id of cart
        :param HMAC: HMAC of cart. Do not use url encoded
        :return: An :class:`~.AmazonCart`.
        """
        if not CartId or not HMAC:
            raise CartException('CartId required for CartClear call')
        response = self.api.CartClear(CartId=CartId, HMAC=HMAC, **kwargs)
        root = objectify.fromstring(response)

        new_cart = AmazonCart(root)
        self._check_for_cart_error(new_cart)

        return new_cart