[Zope] add/delete acl_user in dtml

Greetings, I want to add and delete users using dtml. I found a how-to which indicates I can add a user using: <dtml-let name="'Your_Name'" password="'Your_Password'" roles="'Owner'" domains="''"

<dtml-var "py_addUser(_.None,acl_users,name,password,roles,domains)"> </dtml-let> However, when I try this, I get: Error Type: NameError Error Value: py_addUser Any help would be much obliged. Steve