How to use the sasl.SimpleAuth function in sasl

def _client(self, user, pwd):
        return sasl.SimpleAuth(
            sasl.DigestMD5Password,
            {},
            lambda: user,
            lambda: pwd,
            lambda: authenticator().service_type(),
            lambda: authenticator().host()
        )

def ClientAuth(serv_type, host, username, password):

    return sasl.SimpleAuth(
        sasl.DigestMD5Password,
        {},
        lambda: username,
        lambda: password,
        lambda: serv_type,
        lambda: host
    )

def ServerAuth(serv_type, host, users):

    def user():
        raise NotImplementedError

    def password():
        raise NotImplementedError

    def get_host():
        return host

    return sasl.SimpleAuth(
        sasl.DigestMD5Password,
        users,
        user,
        password,
        lambda: serv_type,
        get_host,
        realm=get_host
    )