Repository: huggingface/transformers
Pull request: add Trainer import to .md in appropriate cell block for training.ipynb transformers_doc

# What does this PR do?

transformers_doc/en/training.ipynb does not import Trainer in the code block

```python
trainer = Trainer(
    model=model,
    args=training_args,
    train_dataset=dataset["train"],
    eval_dataset=dataset["test"],
    compute_metrics=compute_metrics,
)
trainer.train()
```

Which is imported from huggingface/transformers repo docs/source/en/training.md. Added the import in the source .md file.

Current behavior:

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
Cell In[7], line 1
----> 1 trainer = Trainer(
      2     model=model,
      3     args=training_args,
      4     train_dataset=dataset["train"],
      5     eval_dataset=dataset["test"],
      6     compute_metrics=compute_metrics,
      7 )
      8 trainer.train()

NameError: name 'Trainer' is not defined

Expected behavior:

The training should begin. Adding the import directly to transformers_doc/en/training.ipynb fixes the issue, but as mentioned in the pull request prompt: changes should be made in the huggingface/transformers repository.

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Fixes # (issue)

Missing import in transformers_doc/en/training.ipynb: `from transformers import Trainer`.

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Changed files:
filename: docs/source/en/training.md
patch: @@ -111,6 +111,8 @@ training_args = TrainingArguments(
 Create a [`Trainer`] instance and pass it the model, training arguments, training and test datasets, and evaluation function. Call [`~Trainer.train`] to start training.
 
 ```py
+from transformers import Trainer
+
 trainer = Trainer(
     model=model,
     args=training_args,