[Zope] turning off inheritance

[Kyler B. Laird]

I am working on generating a directory from Zope
objects.  There is a folder full of units (other
folders).  These units contain people (more
folders).

Units and people both have contact information
stored in their properties.  How do I detect if a
person has, for example, 'contact_email' set?

I've tried
	<dtml-if "_.hasattr(this(), 'contact_email')">
It succeeds if the person doesn't have
contact_email set but its unit does.  I've also
tried variations of <dtml-with ... only>, with no
success.                                    

Any pointers?  Where could I have found the
answer to this on my own?

Thank you.

--kyler