public void demonstratePNCounter() {
   // #pncounter
   final Cluster node = Cluster.get(system);
   final PNCounter c0 = PNCounter.create();
   final PNCounter c1 = c0.increment(node, 1);
   final PNCounter c2 = c1.increment(node, 7);
   final PNCounter c3 = c2.decrement(node, 2);
   System.out.println(c3.value()); // 6
   // #pncounter
 }