[Zope] No module named GenericUserFolder

Hi, I wanted to follow the hint about customizing the cache of an ZSQL method given in the Zope Book at chapter Relational Databases. When I try to press the Advanced tab of a ZSQL method I get: Error Type: ImportError Error Value: No module named GenericUserFolder Regarding to http://www.zope.org/Members/Zen/GenericUserFolder it seems that this is a remainder from some previous code which should not really belong to Zope 2.6.1 which I'm using. Or is there any other problem? Kind regards Andreas.