'Authorized to be in the chain / generate Invitations'

def is_authorized(self, device=None):

    is_auth = False
    is_auth = (is_auth or (self.zone.signed_by == device))
    is_auth = (is_auth or (self.zone == device.get_zone()))
    is_auth = (is_auth or device.is_trusted())
    return is_auth
