docs: 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())
          )