human
I wrote the below code

    choices = [positive_label, negative_label]
    class ThreeStateAction(argparse.Action, ):
        def __call__(self, parser, namespace, values, option_string=None):
            values = (values or positive_label)
            is_positive = (values.lower() == positive_label.lower())
            is_positive = ((not is_positive) if invert else is_positive)
            set_val = None
            if return_label:
                set_val = (positive_label if is_positive else negative_label)
            else:
                set_val = is_positive
            setattr(namespace, self.dest, set_val)
    params = {'choices': CaseInsensitiveList(choices), 'nargs': '?', 'action': ThreeStateAction}
    return params

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

def three_state_flag(positive_label='true', negative_label='false', invert=False, return_label=False):