Jupyter Notebook: Multiple runs of cell doesn't shut down daemon thread.

[kanding]

Exception ignored in: <bound method _MultiProcessingDataLoaderIter.__del__ of <torch.utils.data.dataloader._MultiProcessingDataLoaderIter object at 0x7f3660250fd0>>
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/dist-packages/torch/utils/data/dataloader.py", line 962, in __del__
    self._shutdown_workers()
  File "/usr/local/lib/python3.6/dist-packages/torch/utils/data/dataloader.py", line 942, in _shutdown_workers
    w.join()
  File "/usr/lib/python3.6/multiprocessing/process.py", line 122, in join
    assert self._parent_pid == os.getpid(), 'can only join a child process'
AssertionError: can only join a child process