;; The following removes a method from running SBCL

(remove-method 
 #'initialize-instance
 (find-method #'initialize-instance '(:after)  (mapcar #'find-class '(monom))))

(remove-method
 #'update-instance-for-different-class
 (find-method #'update-instance-for-different-class '() (mapcar #'find-class '(monom poly))))