_actions possessing the `required` flag and not implicitly optional
    through `nargs` being '*' or '?'

def is_required(action):
    '''
    _actions possessing the `required` flag and not implicitly optional
    through `nargs` being '*' or '?'
    '''
    return not isinstance(action, _SubParsersAction) and (
    action.required == True and action.nargs not in ['*', '?'])