docs: public static <E> String toVerticalString(Counter<E> c, int k, String fmt, boolean swap) {
      PriorityQueue<E> q = Counters.toPriorityQueue(c);
      List<E> sortedKeys = q.toSortedList();
      StringBuilder sb = new StringBuilder();
      int i = 0;
      for (Iterator<E> keyI = sortedKeys.iterator(); keyI.hasNext() && i < k; i++) {
        E key = keyI.next();
        double val = q.getPriority(key);
        if (swap) {
          sb.append(String.format(fmt, key, val));
        } else {
          sb.append(String.format(fmt, val, key));
        }
        if (keyI.hasNext()) {
          sb.append('\n');
        }
      }
      return sb.toString();
    }