[Zope] problem/missunderstanding?? with refresh

[Robert Rottermann]

I created a product that adds new rules to structured text.
To this aim I base a class on Structured Text and add to the rules of the
base class like so:

class DWIClass( StructuredText.DocumentWithImages.__class__ ):
  text_types = StructuredText.DocumentWithImages.text_types
  text_types.insert(1,'doc_named_linkEx' )
  text_types.insert(1,'doc_inner_linkEx' )
  text_types.insert(1,'doc_redPicture' )

My reasoning is that as text_types is a class variable it exists only once.

However when I refresh the product after a change  the above lines are added
each time anew.

Now my questions:
Is my code wrong from a python view of things, or should refresh clear the
whole thing?
Does Python create an instance of the base class and an instance of my
class??

Robert