(make-instance ',class-name ,@(mappend #'list keys args)))
(defmethod inst-metric ((,inst-var ,class-name))
(with-slots (,@args) ,inst-var
(make-instance ',class-name ,@(mappend #'list keys args)))
(defmethod inst-metric ((,inst-var ,class-name))
(with-slots (,@args) ,inst-var