(make-instance 'accept-specializer :media-type arg))
(defmethod sb-pcl:unparse-specializer-using-class
((gf accept-generic-function) (specializer accept-specializer))
(make-instance 'accept-specializer :media-type arg))
(defmethod sb-pcl:unparse-specializer-using-class
((gf accept-generic-function) (specializer accept-specializer))