code: public String obtainAndReturnTicketPoolId(Workflow<?> wf) {
          TicketPool tp = findPool(wf.getClass().getName());
          tp.obtain();
          return tp.getId();
      }
docs: For testing..
  
  @param wf
  For this workflow, the corresponding ticketPool is searched and then a ticket is obtained from this pool.
  @return
  id of the ticket pool.