Using run_language_modeling.py to train an English adapter
# 📚 Migration

## Information

<!-- Important information -->

Model I am using bert-base-multilingual-cased:

Language I am using the model on English:

The problem arises when using:

When I entered the codes in the command line and run, the process just stuck here for a long time and did nothing, I tried many times and it always couldn’t start to train?

![image](https://user-images.githubusercontent.com/40454951/114124128-4af04780-9926-11eb-8241-2ed162171a72.png)



The tasks I am working on is:
* Train an English adapter using this script: https://github.com/Adapter-Hub/adapter-transformers/blob/master/examples/contrib/legacy/run_language_modeling.py
* I wrote this in command line:
* python3 run_language_modeling.py \
--output_dir=xxx \
--model_type=bert \
--model_name_or_path=bert-base-multilingual-cased \
--do_train \
--train_data_file=xxx/a.txt \
--do_eval \
--eval_data_file=xxx/b.txt \
--mlm \
--language en \
--train_adapter \
--adapter_config pfeiffer \
--per_gpu_train_batch_size 4 \
--per_gpu_eval_batch_size 4 \
--learning_rate 5e-5

## Details

<!-- A clear and concise description of the migration issue.
    If you have code snippets, please provide it here as well.
    Important! Use code tags to correctly format your code. See https://help.github.com/en/github/writing-on-github/creating-and-highlighting-code-blocks#syntax-highlighting
    Do not use screenshots, as they are hard to read and (more importantly) don't allow others to copy-and-paste your code.
    -->

## Environment info
<!-- You can run the command `python transformers-cli env` and copy-and-paste its output below.
     Don't forget to fill out the missing fields in that output! -->
 
- `transformers` version:
- Platform:
- Python version:
- PyTorch version (GPU?):
- Tensorflow version (GPU?):
- Using GPU in script?:
- Using distributed or parallel set-up in script?:

<!-- IMPORTANT: which version of the former library do you use? -->
* `pytorch-transformers` or `pytorch-pretrained-bert` version (or branch):


## Checklist

- [ ] I have read the migration guide in the readme.
 ([pytorch-transformers](https://github.com/huggingface/transformers#migrating-from-pytorch-transformers-to-transformers);
  [pytorch-pretrained-bert](https://github.com/huggingface/transformers#migrating-from-pytorch-pretrained-bert-to-transformers))
- [ ] I checked if a related official extension example runs on my machine.

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.