[Zope] How to use methods from OFS?

[Martin Gebert]

Hi!

I'm trying to import and use OFS.content_types.guess_content_type(), 
Zope's method to get content types of files by name or content, in a 
Python script within Zope. But all I get is an Unauthorized error: "You 
are not allowed to access content_types in this context" (even Proxy 
role "Manager" didn't succeed).
I guess invoking OFS modules needs special permissions or even External 
Methods. Is this correct, and can somebody give me a hint/a working 
example how to achieve this?
Thanks a lot! And good night now...

Martin