def __init__(self, *args, **kwargs):
        # type: (Any, Any) -> None
        """__init__(o, sentinel=None, modifier=lambda x: x)"""
        if 'modifier' in kwargs:
            self.modifier = kwargs['modifier']
        elif len(args) > 2:
            self.modifier = args[2]
            args = args[:2]
        else:
            self.modifier = lambda x: x
        if not callable(self.modifier):
            raise TypeError('modify_iter(o, modifier): '
                            'modifier must be callable')
        super(modify_iter, self).__init__(*args)