code: def group_for_policy(self, policy=None):
          
          if policy is None:
              policy = self.context.participant_policy
          return "%s:%s" % (policy.title(), self.context.UID())
docs: Lookup the collective.workspace usergroup corresponding to the
          given policy
  
          :param policy: The value of the policy to lookup, defaults to the
                         current policy
          :type policy: str