(setf (attribute-map occurence) (make-hash-table)))
(defgeneric find-occurence (name)
+ (:method (thing)
+ nil)
(:method ((name symbol))
(find-or-create-occurence name))
- (:method (instance)
+ (:method ((instance standard-object))
(find-or-create-occurence (class-name (class-of instance)))))