anchor.diff:  ;; => T, T, T, T
   
   
  -;; (finalize-inheritance (find-class 'singleton-1))
  -
  -
   (class-slots (find-class 'singleton-1))
   
   (class-direct-slots (find-class 'singleton-1))
  -
  -
   
   (defsingleton singleton-2 (singleton-1)
     ((sl-c)))
  
positive.code: 
  (class-direct-slots (find-class 'singleton-2))
  
  
  )
  
negative.code:   ((sl-1)
     (sl-b)))
  
  (typep (find-class 'singleton-1) 'singleton)
  ;; => T
  
  (subtypep (find-class 'singleton-1) 'singleton)
  ;; => T, T
  
  ;; alternately ...
  (let ((c (find-class 'singleton-1)))
    (multiple-value-bind (st-1 st-2)
        (subtypep c 'singleton)
      (multiple-value-bind (mt-1 mt-2)
  