[Zope] How to exclude Confera messages?

[Loren Stafford]

With Michel's help, I got the following navigation stack method running at
http://209.67.167.51/Quena/Discuss. It no longer causes an error when I
navigate to a Confera message, but it doesn't do the right thing either. Try
it.

What I don't know how to do is test the type of the current object from
inside an <!--#in--> loop. That is, how do I test if sequence-item is a
'Folder', 'Confera Topic', 'Message', or what? Can you help?

-- Thanks
-- Loren

<!-- Start Breadcrumbs -->
<!--#unless expr="PARENTS[0]==PARENTS[-1]"-->
<!--#call "REQUEST.set('reverse_PARENTS', [])"-->
<!--#in PARENTS skip_unauthorized-->
<!--#call "reverse_PARENTS.insert(0, _['sequence-item'])"-->
<!--#/in-->

<!--#in reverse_PARENTS-->
<!--#var sequence-item-->
<!--#if sequence-start--><a href="/">Home</a>
<!--#else-->
 <!--#if sequence-end-->
 &gt;&nbsp;<font size="+1" color="#990000"><b><!--#var
title_or_id--></b></font>
 <!--#else-->
 &gt;&nbsp;<a href="<!--#var absolute_url-->"><!--#var id--></a>
 <!--#/if-->
<!--#/if-->
<!--#/in-->
<!--#/unless-->

<!-- End Breadcrumbs -->