def RegisterHandlerOnce(self,name,handler,typ='',ns='',xmlns=None,makefirst=0, system=0):
        """ Unregister handler after first call (not implemented yet). """
        if not xmlns: xmlns=self._owner.defaultNamespace
        self.RegisterHandler(name, handler, typ, ns, xmlns, makefirst, system)
 Unregister handler after first call (not implemented yet). 
chrome-cordova/gcmServer/xmpp/dispatcher.py