[Zope] programmatic manipulation of Property Sheets

[Mitchell L Model]

Could someone please show an example of the programmatic manipulation 
of property sheets for an instance of a Python class (not ZClass) 
derived from PropertyManager?  I've looked at 
http://www.zope.org/Members/michel/Projects/Interfaces/PropertySheets 
and the pages it points to, which provide most of the information, 
and I'm sure I can read the code enough to figure out the rest, but 
it would be really helpful to have an example of some interesting 
manipulations.  Specifically, I want to add a few property sheets, 
then define a few properties for each of those sheets (with initial 
values).  Ideally, I'd like to do this generically somehow as part of 
my class -- especially the initial values -- rather than having to 
initialize every property of every sheet for each instance.