def set_value(self, format, *args):
        """
        Set new value for config item. The new value may be a string, a printf
format, or NULL. Note that if string may possibly contain '%', or if it
comes from an insecure source, you must use '%s' as the format, followed
by the string.
        """
        return lib.zconfig_set_value(self._as_parameter_, format, *args)