Error when passing --line_by_line to run_mlm.py
I am trying to run the `run_mlm.py` examples/language-modeling using my own data file. It works fine if I don't pass the `--line_by_line` parameter, but if I do, it breaks. 

I can't figure this out using the error trace, can anyone give me a hand?

```
python3 run_mlm.py --model_name_or_path bert-base-uncased --train_file full_dataset_lm_train.txt --validation_file full_dataset_lm_dev.txt --do_train --do_eval --output_dir /tmp/moral_foundation_lm/ --line_by_line
```


```
Traceback (most recent call last):
  File "run_mlm.py", line 446, in <module>
    main()
  File "run_mlm.py", line 322, in main
    load_from_cache_file=not data_args.overwrite_cache,
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/dataset_dict.py", line 303, in map
    for k, dataset in self.items()
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/dataset_dict.py", line 303, in <dictcomp>
    for k, dataset in self.items()
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/arrow_dataset.py", line 1260, in map
    update_data=update_data,
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/arrow_dataset.py", line 157, in wrapper
    out: Union["Dataset", "DatasetDict"] = func(self, *args, **kwargs)
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/fingerprint.py", line 158, in wrapper
    self._fingerprint, transform, kwargs_for_fingerprint
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/fingerprint.py", line 105, in update_fingerprint
    hasher.update(transform_args[key])
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/fingerprint.py", line 57, in update
    self.m.update(self.hash(value).encode("utf-8"))
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/fingerprint.py", line 53, in hash
    return cls.hash_default(value)
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/fingerprint.py", line 46, in hash_default
    return cls.hash_bytes(dumps(value))
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/utils/py_utils.py", line 389, in dumps
    dump(obj, file)
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/utils/py_utils.py", line 361, in dump
    Pickler(file, recurse=True).dump(obj)
  File "/usr/lib/python3.6/pickle.py", line 409, in dump
    self.save(obj)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/homes/pachecog/.local/lib/python3.6/site-packages/datasets/utils/py_utils.py", line 556, in save_function
    obj=obj,
  File "/usr/lib/python3.6/pickle.py", line 610, in save_reduce
    save(args)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python3.6/pickle.py", line 751, in save_tuple
    save(element)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python3.6/pickle.py", line 736, in save_tuple
    save(element)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/homes/pachecog/.local/lib/python3.6/site-packages/dill/_dill.py", line 1129, in save_cell
    pickler.save_reduce(_create_cell, (f,), obj=obj)
  File "/usr/lib/python3.6/pickle.py", line 610, in save_reduce
    save(args)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python3.6/pickle.py", line 736, in save_tuple
    save(element)
  File "/usr/lib/python3.6/pickle.py", line 521, in save
    self.save_reduce(obj=obj, *rv)
  File "/usr/lib/python3.6/pickle.py", line 605, in save_reduce
    save(cls)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/homes/pachecog/.local/lib/python3.6/site-packages/dill/_dill.py", line 1315, in save_type
    obj.__bases__, _dict), obj=obj)
  File "/usr/lib/python3.6/pickle.py", line 610, in save_reduce
    save(args)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python3.6/pickle.py", line 751, in save_tuple
    save(element)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/homes/pachecog/.local/lib/python3.6/site-packages/dill/_dill.py", line 902, in save_module_dict
    StockPickler.save_dict(pickler, obj)
  File "/usr/lib/python3.6/pickle.py", line 821, in save_dict
    self._batch_setitems(obj.items())
  File "/usr/lib/python3.6/pickle.py", line 847, in _batch_setitems
    save(v)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/homes/pachecog/.local/lib/python3.6/site-packages/dill/_dill.py", line 902, in save_module_dict
    StockPickler.save_dict(pickler, obj)
  File "/usr/lib/python3.6/pickle.py", line 821, in save_dict
    self._batch_setitems(obj.items())
  File "/usr/lib/python3.6/pickle.py", line 847, in _batch_setitems
    save(v)
  File "/usr/lib/python3.6/pickle.py", line 521, in save
    self.save_reduce(obj=obj, *rv)
  File "/usr/lib/python3.6/pickle.py", line 634, in save_reduce
    save(state)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python3.6/pickle.py", line 736, in save_tuple
    save(element)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/homes/pachecog/.local/lib/python3.6/site-packages/dill/_dill.py", line 902, in save_module_dict
    StockPickler.save_dict(pickler, obj)
  File "/usr/lib/python3.6/pickle.py", line 821, in save_dict
    self._batch_setitems(obj.items())
  File "/usr/lib/python3.6/pickle.py", line 847, in _batch_setitems
    save(v)
  File "/usr/lib/python3.6/pickle.py", line 476, in save
    f(self, obj) # Call unbound method with explicit self
  File "/homes/pachecog/.local/lib/python3.6/site-packages/dill/_dill.py", line 1148, in save_dictproxy
    raise ReferenceError("%s does not reference a class __dict__" % obj)
ReferenceError: {'help': 'The name of the dataset to use (via the datasets library).'} does not reference a class __dict__
```

Update: this error was present when using Python 3.6.9, it disappeared when using Python 3.7.5
I found the hint at: https://github.com/huggingface/transformers/issues/8212 <|||||>This issue has been automatically marked as stale and been closed because it has not had recent activity. Thank you for your contributions.

If you think this still needs to be addressed please comment on this thread.