[Zope-CMF] How to select"published" documents with discussions "enabled."

[Forum Administrator]

Hello,

I am new to the zope/cmf/plone world, so please bear with me.

I am trying to figure out how to select only those documents
that are (a) in published state and (b) have discussions enabled.

I looked at the News templet and I see:
  tal:define="results 
Python:container.portal_catalog(meta_type='News 
Item',sort_on='created',sort_order='reverse',review_state='published');

I have changed meta_type to Document and am able to list 
documents in published state, but not sure the syntax to
test for the isDiscussionAllowedFor (or a similar) property

Thanks much for any pointers, a code snippet, or just a link to a 
relevant page somewhere.

TIA,

Nowar.org Forum Admin