[Zope] Add python class to Zope.

Hi! I found some python sources which declared "class" inside. I tried to call the function inside this class with external method and python script but it didn't work out. For examples: Guestbook.py class Guestbook: def __init__ .... def signGuestBook .... def feedBack. .. How can I call the function "feedBack" to Zope? Thank you! pattreeya .