def _is_include_directive(entry):
    return (isinstance(entry, list) and
            len(entry) == 2 and entry[0] == 'include' and
            isinstance(entry[1], str))
Should return one valid email in a list.
dataset/ETHPy150Open letsencrypt/letsencrypt/certbot-nginx/certbot_nginx/parser.py/_is_include_directive--crossover with--dataset/ETHPy150Open ofa/connect/open_connect/accounts/tests/test_forms.py/InviteFormTest.test_clean_emails_one_email