I have trained a BertForSequenceClassification model, saved the model and tokenizer by
model.save_pretrained('output_mlm_cls')
tokenizer.save_pretrained('output_mlm_cls')

I’m trying to run run_mlm_wwm.py and I want it to load the saved model above:
python run_mlm_wwm.py \
    --model_name_or_path /path/to/output_mlm_cls \
    --train_file /path/to/my_data.txt \
    --do_train \
    --output_dir /output_dir

Then I get this error message:

Traceback (most recent call last):
File “run_mlm_wwm.py”, line 408, in 
main()
File “run_mlm_wwm.py”, line 367, in main
train_result = trainer.train(resume_from_checkpoint=checkpoint)
File “/home/cl/jungmin-c/.pyenv/versions/anaconda3-5.1.0/envs/jp/lib/python3.7/site-packages/transformers/trainer.py”, line 1066, in train
self._load_state_dict_in_model(state_dict)
File “/home/cl/jungmin-c/.pyenv/versions/anaconda3-5.1.0/envs/jp/lib/python3.7/site-packages/transformers/trainer.py”, line 1387, in _load_state_dict_in_model
if set(load_result.missing_keys) == set(self.model._keys_to_ignore_on_save):
TypeError: ‘NoneType’ object is not iterable

I could not figure out what is wrong with my approach. I would greatly appreciate your suggestion.
Thank you!