@classmethod
def _normalize_items(cls, item):
    """Recursively transform sets into lists"""
    if type(item) in [list, set, tuple]:
        return list(map(cls._normalize_items, item))
    elif isinstance(item, dict):
        return dict(map(lambda i: (i[0], cls._normalize_items(i[1])), item.
            items()))
    else:
        return item
