[Zope] Structured Text's "DocumentWithImages" class

Hi there, I was just looking through the change notes for Zope 2.6.0a, and came across something about "Structured Text's "DocumentWithImages" class" - I searched zope.org, the zope cookbook, and the mailing list archives, and couldn't find any reference to DocumentWithImages - can someone point me to the correct documentation? This sounds interesting. Thanks, Am