[Zope] Convert Photos to ExtImage store

I have a few PhotoFolders containing Photos that are stored in the ZODB which I would like to convert to ExtImage storage. Since the number is large enough to make a manual process painful, I'd like to write a conversion script. Seems simple enough in principle, but I'm having trouble getting started. First, how do you use manage_addPhoto()? I assumed that photo_folder.manage_addPhoto() would work, but I get AttributeError: manage_addPhoto Ideally, the script would operate on a PhotoFolder object, say, making a new PhotoFolder, then creating all the new Photos based on the old ones. I can manually delete the old folder and rename the new one. Thanks, David Zope 2.7.0/Python 2.3.2 Photo 1.2.3