[Zope] Add new property to a class

[Luis Machado]

Having defined a class using python like this one:

from OFS import ObjectManager, SimpleItem

class Plant(ObjectManager.ObjectManager, SimpleItem.SimpleItem):
   """A plant"""

   def __init__(self, name, responsible):
	 "Inits the product with default values"
	 self.name = name
         self.responsible = responsible
         self.areas = {}

you create a few instances, and later you want to add more properties to
the same class, for example:

   def __init__(self, name, responsible, address):
	 "Inits the product with default values"
	 self.name = name
         self.responsible = responsible
         self.areas = {}
         self.address = address

Is there a way to programatically modify the existing instances and add
this new property to them.

Any help will be appreciated.

Luis