def invalidate(to_invalidate):
    """ Invalidate the indicated objects.

        o If 'to_invalidate' is a string, treat it as an OID.

        o Otherwise, iterate over it as a sequence of OIDs.

        o Any OID corresponding to a p-class will cause the corresponding
            p-class to be removed from the cache.

        o For all other OIDs, ghostify the corrsponding object and
            remove it from the ring.
        """
