docs: public static void main(String[] args) {
      FixedPrioritiesPriorityQueue<String> pq = new FixedPrioritiesPriorityQueue<String>();
      System.out.println(pq);
      pq.add("one",1);
      System.out.println(pq);
      pq.add("three",3);
      System.out.println(pq);
      pq.add("one",1.1);
      System.out.println(pq);
      pq.add("two",2);
      System.out.println(pq);
      System.out.println(pq.toString(2));
      while (pq.hasNext()) {
        System.out.println(pq.next());
      }
    }