[Zope] ZClass inheritance and contained objects (Zope 2.3.0)

[Oliver Frommel]

Hello,

a similar problem as the one with property inheritance I have now with objects
contained by a ZClass. I add a DTML Method to a ZClass in the Product Manager.
Is this DTML Method now supposed to show up in the Contents tab of a ZClass
Instance? At least it doesn't here which I found somehow strange. 
On the other hand if I try to add a DTML Method with the same name (as the one
added to the ZClass) to the Instance I get an error:

Error Type: Bad Request
Error Value: The id "text_obj" is invalid--it is already in use.

is this the default behaviour? If yes, how can I make ZClass Instances contain
certain objects on creation?

thanks
--Oliver