When training with Multi-Node Multi-GPU the worker 2 has TypeError: 'NoneType' object
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Hi ! Thanks for reporting
I was able to reproduce this issue. This was caused by missing split infos if a worker reloads the cache of the other worker.

I just opened https://github.com/huggingface/datasets/pull/2137 to fix this issue The PR got merged :)
Feel free to try it out on the `master` branch Sorry for the late reply.  
Now everything just works well XD
version: 1.5.0
met a very strange error, I am training large scale language model, and need train on 2 machines(workers).
And sometimes I will get this error `TypeError: 'NoneType' object is not iterable`
This is traceback
```

71 |   | Traceback (most recent call last):
-- | -- | --
72 |   | File "run_gpt.py", line 316, in <module>
73 |   | main()
74 |   | File "run_gpt.py", line 222, in main
75 |   | delimiter="\t", column_names=["input_ids", "attention_mask", "chinese_ref"])
76 |   | File "/data/miniconda3/lib/python3.7/site-packages/datasets/load.py", line 747, in load_dataset
77 |   | use_auth_token=use_auth_token,
78 |   | File "/data/miniconda3/lib/python3.7/site-packages/datasets/builder.py", line 513, in download_and_prepare
79 |   | self.download_post_processing_resources(dl_manager)
80 |   | File "/data/miniconda3/lib/python3.7/site-packages/datasets/builder.py", line 673, in download_post_processing_resources
81 |   | for split in self.info.splits:
82 |   | TypeError: 'NoneType' object is not iterable
83 |   | WARNING:datasets.builder:Reusing dataset csv (/usr/local/app/.cache/huggingface/datasets/csv/default-1c257ebd48e225e7/0.0.0/2960f95a26e85d40ca41a230ac88787f715ee3003edaacb8b1f0891e9f04dda2)
84 |   | Traceback (most recent call last):
85 |   | File "/data/miniconda3/lib/python3.7/runpy.py", line 193, in _run_module_as_main
86 |   | "__main__", mod_spec)
87 |   | File "/data/miniconda3/lib/python3.7/runpy.py", line 85, in _run_code
88 |   | exec(code, run_globals)
89 |   | File "/data/miniconda3/lib/python3.7/site-packages/torch/distributed/launch.py", line 340, in <module>
90 |   | main()
91 |   | File "/data/miniconda3/lib/python3.7/site-packages/torch/distributed/launch.py", line 326, in main
92 |   | sigkill_handler(signal.SIGTERM, None)  # not coming back
93 |   | File "/data/miniconda3/lib/python3.7/site-packages/torch/distributed/launch.py", line 301, in sigkill_handler
94 |   | raise subprocess.CalledProcessError(returncode=last_return_code, cmd=cmd)

```
On worker 1 it loads the dataset well, however on worker 2 will get this error. 
And I will meet this error from time to time, sometimes it just goes well.
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