[Zope] why cant i import types ?

[Declan Shanaghy]

Can someone tell me why i cant import types into my python
script in CMF?
When i put either of the following lines as the first line
of my script i get the error that follows

from types import * - produces
Error Type: ImportError
Error Value: "from types import *" is not allowed

from types import ListType - produces
Error Type: ImportError
Error Value: import of "ListType" from "types" is
unauthorized. You are not allowed to access ListType in
this context