def order_by_descending(self, key):
        """
        Returns new Enumerable sorted in descending order by given key
        :param key: key to sort by as lambda expression
        :return: new Enumerable object
        """
        if key is None:
            raise NullArgumentError(u"No key for sorting given")
        kf = [OrderingDirection(key, reverse=True)]
        return SortedEnumerable3(kf, self._data)
Returns new Enumerable sorted in descending order by given key
        :param key: key to sort by as lambda expression
        :return: new Enumerable object