code: def add(self, nb = 1, name = None, xid = None):
          
          for x in xrange(nb):
              self.count_lock.acquire()
              if self.workers >= self.max_workers:
                  self.count_lock.release()
                  continue
              self.workers += 1
              if xid is None:
                  xid = self.workers
              self.count_lock.release()
              self.kill_event.clear()
              w = WorkerThread(xid, self)
              w.setName(self.get_name(xid, name))
              w.start()
docs: Create one or many workers.