AttributeError: 'Sst2Processor' object has no attribute 'tfds_map'
## 🐛 Bug

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hey I just wanted to test BERT for sst2. I have just changed official example script to this: 

```
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/sst2')

# Prepare dataset for GLUE as a tf.data.Dataset instance
train_dataset = glue_convert_examples_to_features(data['train'], tokenizer, max_length=128, task='sst-2')
valid_dataset = glue_convert_examples_to_features(data['validation'], tokenizer, max_length=128, task='sst-2')
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)

# Load the TensorFlow model in PyTorch for inspection
model.save_pretrained('./save/')
pytorch_model = BertForSequenceClassification.from_pretrained('./save/', from_tf=True)

# Quickly test a few predictions - MRPC is a paraphrasing task, let's see if our model learned the task
sentence_0 = "I didn't think this was as absolutely horrible."
inputs_1 = tokenizer.encode_plus(sentence_0, add_special_tokens=True, return_tensors='pt')


pred_1 = pytorch_model(inputs_1['input_ids'], token_type_ids=inputs_1['token_type_ids'])[0].argmax().item()
print("sentence_1 is", pred_1)

```
I'm using  google colab with tensorflow2.0 . the error is :

AttributeError: 'Sst2Processor' object has no attribute 'tfds_map'

@abb4s A workaround would be downgrading `transformers` to `2.2.0`. It worked for me that way.<|||||>Indeed, this was an error introduced by #1548. It was patched by 1efc208. Thank you for raising this issue! <|||||>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.
