docs: def _spawn_threads(self):
          '''
          Internal method.  Creates threads to handle low-level
          network receive.
          '''
          for devname,pdev in self._pcaps.items():
              t = threading.Thread(target=LLNetReal._low_level_dispatch, args=(pdev, devname, self._pktqueue))
              t.start()
              self._threads.append(t)