docs: public Ticket add(long delay, TimerHandler handler, Object... args)
      {
          if (handler == null) {
              return null;
          }
          Utils.checkArgument(delay > 0, "Delay of a ticket has to be strictly greater than 0");
          final Ticket ticket = new Ticket(this, now(), delay, handler, args);
          insert(ticket);
          return ticket;
      }