Return a list of the items with their final scores.

        The final score of each item is its average score multiplied by the
        square root of its length.  This reduces to sum * len^(-1/2).

def scores(self):
        """Return a list of the items with their final scores.

        The final score of each item is its average score multiplied by the
        square root of its length.  This reduces to sum * len^(-1/2).
        """
        return map(
            lambda x: (x[0], sum(x[1]) * len(x[1]) ** -.5),
            iter(self.items.viewitems())
        )