code: private static String keyToGoWithElementsString(String label, DuplicateGroupedAndTyped elements) {
      /*
       * elements.toString(), which the caller is going to use, includes the homogeneous type (if
       * any), so we don't want to include it here. (And it's better to have it in the value, rather
       * than in the key, so that it doesn't push the horizontally aligned values over too far.)
       */
      return lenientFormat("%s (%s)", label, elements.totalCopies());
    }
docs: /*
  Fact keys like "missing (1)" go against our recommendation that keys should be fixed strings.
  But this violation lets the fact value contain only the elements (instead of also containing
  the count), so it feels worthwhile.