Facing Issue while running `run_tf_multiple_choice.py` from examples
Author: bhadreshpsavani
Pull request: no

## Environment info
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- `transformers` version: 4.4.0.dev0
- Platform: Colab
- Python version: NA
- PyTorch version (GPU?): NA
- Tensorflow version (GPU?):
- Using GPU in script?: No
- Using distributed or parallel set-up in script?: No

### Who can help
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## Information

I was trying to train `bert-base-cased` on Multiple Choice task with below script provided on Readme of the task
```
export SWAG_DIR=/path/to/swag_data_dir
python ./examples/multiple-choice/run_tf_multiple_choice.py \
--task_name swag \
--model_name_or_path bert-base-cased \
--do_train \
--do_eval \
--data_dir $SWAG_DIR \
--learning_rate 5e-5 \
--num_train_epochs 3 \
--max_seq_length 80 \
--output_dir models_bert/swag_base \
--per_gpu_eval_batch_size=16 \
--per_device_train_batch_size=16 \
--gradient_accumulation_steps 2 \
--overwrite_output
```
I got below error
```
Invalid argument: ValueError: `generator` yielded an element of shape (4, 1, 80) where an element of shape (None, None) was expected.
Traceback (most recent call last):

  File "/usr/local/lib/python3.7/dist-packages/tensorflow/python/ops/script_ops.py", line 249, in __call__
    ret = func(*args)

  File "/usr/local/lib/python3.7/dist-packages/tensorflow/python/autograph/impl/api.py", line 620, in wrapper
    return func(*args, **kwargs)

  File "/usr/local/lib/python3.7/dist-packages/tensorflow/python/data/ops/dataset_ops.py", line 938, in generator_py_func
    (ret_array.shape, expected_shape))

ValueError: `generator` yielded an element of shape (4, 1, 80) where an element of shape (None, None) was expected.
```
The problem arises when using:
* [x] the official example scripts: (give details below)
* [ ] my own modified scripts: (give details below)

The tasks I am working on is:
* [x] an official GLUE/SQUaD task: (give the name) swag
* [ ] my own task or dataset: (give details below)

## To reproduce

Steps to reproduce the behavior:

Follow this colab [Notebook ](https://github.com/bhadreshpsavani/UnderstandingNLP/blob/master/CheckingTFScripts.ipynb) to run the script and reproduce the issue.

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## Expected behavior

It should execute the script and train the model without the given error.

Note: The colab notebook given in the readme is not working, It's outdated maybe!
**I removed `--logging-dir logs \` from the script because it was giving me another error**

Tagging SMEs:
@LysandreJik @jplu

Comments:
Even for the `run_tf_squad.py`  script, I am facing the issue. 

Here is the [colab notebook](https://github.com/bhadreshpsavani/UnderstandingNLP/blob/master/Check_run_tf_squad.ipynb) with issue and Traceback logs

Is there anything else I need to use while running the script?

Hello!

The multiple choice example needs to be reworked. A PR to fix the squad example is available https://github.com/huggingface/transformers/pull/10275. Be aware that some arguments are not implemented on the TF side.

The TF examples are under rework and should become more reliable in a near future.

I am closing this issue since it is already WIP