[Zope] replacing image without manage_upload

Hi, I have a class with an dictionary containing on or more classes. The main class contains an image and the classes in the dictionary can contain images. I want to replace the content of the image in the main class with one of the classes in the dictionary. This won't work: self.afbeelding=self.edits[edit_id].afbeelding_edit. Somewhere the imagetype get lost. Any idea? Henny