Recursion 的常用写法

walk.py

 def get_labels(model, *filter_options):
    unnest_lables = db.session.query(func.unnest(getattr(model, 'labels'))).filter(*filter_options)

    labels = set()
    def _walk(iterable):
        for item in iterable:
            if isinstance(item, tuple):
                _walk(item)
            else:
                labels.add(item)

    _walk(unnest_lables)
    return list(labels)