[Zope] Calling a sequence-item functions

I would like to call a python function from a sequence item: <dtml-in "Catalog(page_type='issuedtml')" prefix="x"> 1: <dtml-var expr="x_item.title"> 2: <dtml-var expr="x_item.GetTitle()"> 3: <dtml-var expr="x_item.GetObjectTitle(x_item)"> in class TrackerSupport I have: def GetTitle(self) return self.title def GetObjectTitle(self,object) return object.title 1: gives the correct title 2: gives the title from the page where the dtml code is in. 3: gives the correct title. Why is GetTitle not working? Where can I find some info on this subject? Wim