;; only in the case where the class is its own chain head. There are two
;; subcases: if there are no direct superclasses at all, then the class is
;; its own root; otherwise, it clearly can't be the root and the omission
;; only in the case where the class is its own chain head. There are two
;; subcases: if there are no direct superclasses at all, then the class is
;; its own root; otherwise, it clearly can't be the root and the omission