[Zope] AttributeError __getslice__ from Zope Construction Kit book

Hello. I've been through the Zope "Web Application Construction Kit" book tutorial, chapter 5, "Building a Portal and Adding Serices" "Creating a Type with ZClasses", twice now. Each time, when attempting to add the new ZClass object in a user folder, this error is generated: Error Type AttributeError Error Value __getslice__ Does anyone have any sense of what this means and how to fix it? My Zope is 2.6.0 running on Redhat 8. Thanks. Harlow Pinson Indepth Learning Email: hpinson@indepthl.com Web: http://www.indepthl.com Voice: 505-994-2135 FAX: 208-475-7678