Quick tour TF 2.0 
# 🐛 Bug

## Information

I am trying **Quick tour TF 2.0**.

The problem arises when using a quick example: **How a TensorFlow 2.0 model can be trained in 12 lines of code**:

```python
import tensorflow as tf
import tensorflow_datasets
from transformers import *

# Load dataset, tokenizer, model from pretrained model/vocabulary
tokenizer = BertTokenizer.from_pretrained('bert-base-cased')
model = TFBertForSequenceClassification.from_pretrained('bert-base-cased')
data = tensorflow_datasets.load('glue/mrpc')

# Prepare dataset for GLUE as a tf.data.Dataset instance
train_dataset = glue_convert_examples_to_features(data['train'], tokenizer, max_length=128, task='mrpc')
valid_dataset = glue_convert_examples_to_features(data['validation'], tokenizer, max_length=128, task='mrpc')
train_dataset = train_dataset.shuffle(100).batch(32).repeat(2)
valid_dataset = valid_dataset.batch(64)

# Prepare training: Compile tf.keras model with optimizer, loss and learning rate schedule
optimizer = tf.keras.optimizers.Adam(learning_rate=3e-5, epsilon=1e-08, clipnorm=1.0)
loss = tf.keras.losses.SparseCategoricalCrossentropy(from_logits=True)
metric = tf.keras.metrics.SparseCategoricalAccuracy('accuracy')
model.compile(optimizer=optimizer, loss=loss, metrics=[metric])

# Train and evaluate using tf.keras.Model.fit()
history = model.fit(train_dataset, epochs=2, steps_per_epoch=115,
                    validation_data=valid_dataset, validation_steps=7)
```
which produces the output below:
```python
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-4-ea94e17f2f79> in <module>()
      1 tokenizer = BertTokenizer.from_pretrained('bert-base-cased')
----> 2 model = TFBertForSequenceClassification.from_pretrained('bert-base-cased')
      3 data = tensorflow_datasets.load('glue/mrpc')

NameError: name 'TFBertForSequenceClassification' is not defined
```



The above behavior can be reproduced using this [Colab ](https://colab.research.google.com/drive/1aAmOVlvkuP9PLOuGKVx7-k0vsVBoD506)notebook.

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Any help will be much appreciated.

Our models are TensorFlow 2.x only, while your notebook is in TensorFlow 1.x:

```
The default version of TensorFlow in Colab will soon switch to TensorFlow 2.x.
We recommend you upgrade now or ensure your notebook will continue to use TensorFlow 1.x via the %tensorflow_version 1.x magic: more info.
```

You can use the following command at the start of your notebook to use TensorFlow 2.x:

```
%tensorflow_version 2.x
```<|||||>@LysandreJik thank you.