[Zope3-Users] ForbiddenAttribute error when adding a container

[baiju m]

Hi all,
         I am Baiju from Kerala (India), and I am new to this list.

Recently I started learning Zope3, to play with it I am developing a 
small app. The latest tarball is available here :
http://baijum81.freezope.org/zissue/zissue-0.1.1.tar.bz2

When I am trying to add a 'Comment' (Implemented using BTreeContainer)
An error occur (in browser): A system error occurred. 
Can anyone give a pointer, how to fix it.

...
  File "/usr/local/Zope-3.1.0c1/lib/python/zope/app/container/size.py",
line 38, in sizeForDisplay
    num_items = len(self._container)
ForbiddenAttribute: ('__len__', <zissue.zissuetracker.comment.Comment
object at 0x4164eb2c>)
192.168.1.10 - zope.manager [13/Sep/2005:16:33:58 +0530] "GET
/zit/ZissueTracker/MainProduct/Component/Zissue/@@contents.html
HTTP/1.1" 500 311
"http://192.168.1.15:7080/zit/ZissueTracker/MainProduct/Component/Zissue/+/AddComment.html="
"Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.8) Gecko/20050517
Firefox/1.0.4 (Debian package 1.0.4-2)"
...


Thanks,
Baiju M