[Zope-PAS] how??

[javi lopez]

i am doing a plugin for pas, i did this method but it don´t work:

security.declarePrivate('authenticateCredentials')
    def authenticateCredentials(self, credentials):
        """ Authentication Part

        login = credentials.get( 'login' )
        password = credentials.get( 'password' )

        if login is None or password is None:
            return None
        return login, login

what wrong???