[Zope] Deleting a file in Python

[zozer at cercy.net]

I'm reading the zope book, 2.6. And I've worked through the ZopeZoo
tutorial in chapter 11. I want to make it possible to delete entries in
the GuestBook via its web interface. It uses a python script to create the
file with the line:
context.manage_addProduct['OFSP'].manage_addFile(id,
                                         title="", file=comments)

I assume I could write something like:

context.manage_deleteProduct['OFSP'].manage_removeFile(id)

or maybe:

context.manage_addProduct['OFSP'].manage_deleteFile(id)

but I can't figure out where context.* is documented.