def gmtime_adj_notAfter(self, amount):
        """
        Adjust the time stamp on which the certificate stops being valid.

        :param int amount: The number of seconds by which to adjust the
            timestamp.
        :return: ``None``
        """
        if not isinstance(amount, int):
            raise TypeError("amount must be an integer")

        notAfter = _lib.X509_get_notAfter(self._x509)
        _lib.X509_gmtime_adj(notAfter, amount)
Adjust the time stamp on which the certificate stops being valid.

        :param int amount: The number of seconds by which to adjust the
            timestamp.
        :return: ``None``