human
I wrote the below code

    if (on_existing not in ('nothing', 'delete', 'skip')):
        raise RuntimeError("The    value    of    'on_existing'    can    only    be    one    of,    'nothing',    'delete'    and    'skip'")
    if (not isinstance(delete, bool)):
        raise RuntimeError("The    value    of    'delete'    can    only    be    'True'    or    'False'")
    def decorator(func):
        @functools.wraps(func)
        def wrap(cls):
            log.debug('Creating    system    user    {0!r}'.format(username))
            create_user = cls.run_function('user.add', [username])
            log.debug('Creating    system    group    {0!r}'.format(group))
            create_group = cls.run_function('group.add', [group])
            if (not create_user):
                log.debug('Failed    to    create    system    user')
                if (on_existing == 'skip'):
                    cls.skipTest('Failed    to    create    system    user    {0!r}'.format(username))
                if (on_existing == 'delete'):
                    log.debug('Deleting    the    system    user    {0!r}'.format(username))
                    delete_user = cls.run_function('user.delete', [username, True, True])
                    if (not delete_user):
                        cls.skipTest('A    user    named    {0!r}    already    existed    on    the    system    and    re-creating    it    was    not    possible'.format(username))
                    log.debug('Second    time    creating    system    user    {0!r}'.format(username))
                    create_user = cls.run_function('user.add', [username])
                    if (not create_user):
                        cls.skipTest('A    user    named    {0!r}    already    existed,    was    deleted    as    requested,    but    re-creating    it    was    not    possible'.format(username))
            if (not create_group):
                log.debug('Failed    to    create    system    group')
                if (on_existing == 'skip'):
                    cls.skipTest('Failed    to   ...

What's a good function header?
assistant
#Here's a good function header.

def with_system_user_and_group(username, group, on_existing='delete', delete=True):