Error on fine-tuning XLM like model on SQUaD like dataset
# 🐛 Bug

## Information

I am trying to fine-tune the model [xlm-mlm-100-1280](https://huggingface.co/xlm-mlm-100-1280) on SQuAD v1 dataset like (tydiQA) with the script provided for this task (transformers/examples/run_squad.py) and I get the following error:

```python
Epoch:   0% 0/5 [00:00<?, ?it/s]
Iteration:   0% 0/2383 [00:00<?, ?it/s]Traceback (most recent call last):
  File "/content/transformers/examples/run_squad.py", line 829, in <module>
    main()
  File "/content/transformers/examples/run_squad.py", line 768, in main
    global_step, tr_loss = train(args, train_dataset, model, tokenizer)
  File "/content/transformers/examples/run_squad.py", line 204, in train
    outputs = model(**inputs)
  File "/usr/local/lib/python3.6/dist-packages/torch/nn/modules/module.py", line 532, in __call__
    result = self.forward(*input, **kwargs)
TypeError: forward() got an unexpected keyword argument 'cls_index'

Epoch:   0% 0/5 [00:00<?, ?it/s]
Iteration:   0% 0/2383 [00:00<?, ?it/s]
```

## To reproduce
```bash
git clone https://github.com/huggingface/transformers
pip install -q ./transformers

# wget "your SQuAD v1 like dataset

python /content/transformers/examples/run_squad.py \
  --model_type xlm \
  --model_name_or_path xlm-mlm-100-1280 \
  --do_lower \
  --do_train \
  --do_eval \
  --train_file /content/dataset/tydiqa-goldp-v1.0-train.json \
  --predict_file /content/dataset/tydiqa-goldp-v1.0-dev.json \
  --per_gpu_train_batch_size 24 \
  --per_gpu_eval_batch_size 128 \
  --learning_rate 3e-5 \
  --num_train_epochs 5 \
  --max_seq_length 384 \
  --doc_stride 128 \
  --output_dir /content/model_output \
  --overwrite_output_dir \
  --save_steps 2000 \
  --threads 400
```

## 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: 2.7.0
- Platform: Linux-4.14.137+-x86_64-with-Ubuntu-18.04-bionic
- Python version: 3.6.9
- PyTorch version (GPU?): 1.4.0 (True)
- Tensorflow version (GPU?): 2.2.0-rc1 (True)
- Using GPU in script?: Yes. Nvidia Tesla P100
- Using distributed or parallel set-up in script?: No

Hi, any follow-up in this thread? I have received the same error with yours, but a different parameter  'model_name_or_path = xlm-mlm-tlm-xnli15-1024' is used in my experiment.<|||||>I had to revert all the way to 2.5.1 to get this to work (xlnet-base fine-tuning on SQuAD 1.1), FWIW, so it's been broken for a bit...<|||||>Thanks @nelson-liu <|||||>Cc @julien-c <|||||>> I had to revert all the way to 2.5.1
Thanks @nelson-liu
using `run_squad.py` at `huggingface/transformers/v2.5.1/examples`
https://raw.githubusercontent.com/huggingface/transformers/v2.5.1/examples/run_squad.py<|||||>I encountered a similar error fine-tuning a RoBERTa model on a SWAG-like dataset using the example scripts. The problem appears to be that the transformers.Trainer object defined [here](https://github.com/huggingface/transformers/blob/master/src/transformers/trainer.py) unpacks all the properties of the InputFeatures as arguments to the model's `forward`, like so:
```
for k, v in inputs.items():
    inputs[k] = v.to(self.args.device)
    ...
    outputs = model(**inputs)
```
The problem is that the InputFeatures have properties like example_id that are not valid keyword args for `forward`. (Same problem for this ticket: SquadFeatures has cls_index). 

As a workaround, I'm removing the example_id property from InputFeatures. Long-term, maybe the Trainer should be more selective about which arguments it passes?
<|||||>`run_squad.py` doesn't currently use the Trainer so this is probably a distinct issue, @steeter-cyclist .<|||||>Same query as @andyweizhao. Any updates? Reverting to v2.5.1 throws ImportError: cannot import name 'MODEL_FOR_QUESTION_ANSWERING_MAPPING'<|||||>This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
<|||||>Still occurs
```
Iteration:   0%|                                                                         | 0/44511 [00:00<?, ?it/s]
Epoch:   0%|                                                                                 | 0/4 [00:00<?, ?it/s]
Traceback (most recent call last):
  File "run_squad.py", line 820, in <module>
    main()
  File "run_squad.py", line 763, in main
    global_step, tr_loss = train(args, train_dataset, model, tokenizer)
  File "run_squad.py", line 202, in train
    outputs = model(**inputs)
  File "C:\Users\erann\AppData\Local\Programs\Python\Python38\lib\site-packages\torch\nn\modules\module.py", line 72
2, in _call_impl
    result = self.forward(*input, **kwargs)
TypeError: forward() got an unexpected keyword argument 'cls_index'
```

https://github.com/huggingface/transformers/issues/6360 shows stale-bot already kicked into action in there as well