[Zope] Inheriting from ObjectManager

Hello, I am using Zope 2.3.3. In order my class ChannelFolder can contain other objects, I subclass it from ObjectManager. All works fine until I try to create other instances of the ChannelFolder class IN a ChannelFolder instance (let's call the latter A). In that case, these ChannelFolder objects are not created in A as expected but in the container of A (so, one level too high). I am using the following instructions: newChannelFolder=ChannelFolder(id, title, description) self._setObject(id, newChannelFolder) to create and place the ChannelFolder objects in their container. Any idea of what has to be done so it works properly ? Thanks in advance, Philippe Bocquillon