[plt-scheme] can't find class class%

I went to extend class class%, and derive a new set of objects from
the extended class:

(define bean-class%
  (class class%
    (super-new)
    (init-field (bean-xpm ""))
    (public bean-image)
    (define-values (bean-image) (lambda (xpm) (set! bean-xpm xpm)))
    (init-field (bean-description-var ""))
    (public bean-description)
    (define-values (set-bean-description!) (lambda (desc) (set!
bean-desecription-var desc)))
    (init-field (bean-snip-var (lambda () void)))
    (public bean-snip)
    (define-values (bean-snip) (lambda (snip) (set! bean-snip-var snip)))))

But I can't find the class class% in the system or in the docs.  I
know the mzscheme OOP does not implement the full MOP, Is this one of
the MOP features that was decided against in the mzscheme OOP?

Corey