#define BUYAssertCheckout(checkout) BUYAssert([(checkout) hasToken], @"Checkout assertion failed. Checkout must have a valid token associated with it.")
#define BUYAssertToken(checkoutToken) BUYAssert((checkoutToken), @"Checkout assertion failed. Checkout must have a valid token associated with it.")
#define BUYAssertCheckout(checkout) BUYAssert([(checkout) hasToken], @"Checkout assertion failed. Checkout must have a valid token associated with it.")