[Zope] Why is index_html() called instead of __call__()?

[Kyler Laird]

I've been trying to use PropertyFolder for awhile now.  Almost
all of my projects depend heavily on functionality that it
would make *much* cleaner.

I'm running a fairly standard Debian distribution of Zope, but
I have to modify PropertyFolder to define index_html() instead
of __call__(), otherwise the "object_type" renderer is ignored.
I'm not sure PropertyFolder is to blame.

Should an object's __call__() method be used to render it?  Any
ideas why index_html() might be used instead?  Where could I go
to track down the misbehavior?  I'd like to fix this so I can
move on to some enhancements.

Thank you.

--kyler