docs: public double spelling(final String source) {
      assert (source.startsWith("|"));
      assert (source.endsWith("|"));
      WordSpelling original = new WordSpelling(source);
      WordSpelling corrected = IntStream.range(0, 1).mapToObj(i -> buildCorrection(original)).min(Comparator.comparingDouble(x -> x.sum)).get();
      return corrected.sum;
    }