(define-method-combination + :identity-with-one-argument t)
(define-method-combination and :identity-with-one-argument t)
(define-method-combination append :identity-with-one-argument nil)
(define-method-combination + :identity-with-one-argument t)
(define-method-combination and :identity-with-one-argument t)
(define-method-combination append :identity-with-one-argument nil)