code: def start(self):
          
          if self.working:
              return
          self.working = True
          for i in range(self.num_workers):
              w = threading.Thread(
                  name="Worker Thread #{i}".format(i=i),
                  target=self._worker,
                  )
              w.daemon = True
              w.start()
              self.workers.append(w)
docs: Starts the worker threads