unk handling in v3.0 different than v2.0?
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## Details
<!-- Description of your issue -->
I have this problem in runing my code in transformers3.0.2,
Trainable parameters: 102274668
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Traceback (most recent call last):
  File "train.py", line 92, in <module>
    run('./configs/base_config.json')
  File "train.py", line 88, in run
    main(config)
  File "train.py", line 66, in main
    trainer.train()
  File "/DATA2/disk1/wangbingchen/project/ccks2020-task8-pytorch/base/base_trainer.py", line 67, in train
    result = self._train_epoch(epoch)
  File "/DATA2/disk1/wangbingchen/project/ccks2020-task8-pytorch/trainer/trainer.py", line 59, in _train_epoch
    for batch_idx, batch_data in enumerate(self.train_iter):
  File "/home/wangbingchen/wangbingchen/anaconda3/lib/python3.7/site-packages/torch/utils/data/dataloader.py", line 345, in __next__
    data = self._next_data()
  File "/home/wangbingchen/wangbingchen/anaconda3/lib/python3.7/site-packages/torch/utils/data/dataloader.py", line 385, in _next_data
    data = self._dataset_fetcher.fetch(index)  # may raise StopIteration
  File "/home/wangbingchen/wangbingchen/anaconda3/lib/python3.7/site-packages/torch/utils/data/_utils/fetch.py", line 47, in fetch
    return self.collate_fn(data)
  File "/DATA2/disk1/wangbingchen/project/ccks2020-task8-pytorch/data_process/military_data_process.py", line 179, in collate_fn
    text_token_ids = torch.LongTensor(np.array(text_token_ids))
TypeError: can't convert np.ndarray of type numpy.object_. The only supported types are: float64, float32, float16, int64, int32, int16, int8, uint8, and bool.
this is the problem of embedding length.But when I run this code in transformers2.11,everything is well.So,I want to ask the difference of transformers2.11 and transformers3.0.2.Thanks very much!
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**A link to original question on the forum/Stack Overflow**:
Hey @BCWang93, can you post a reproducible code snippet? It would be great if we could just copy paste your code and see the same error you post here :-) <|||||>> Hey @BCWang93, can you post a reproducible code snippet? It would be great if we could just copy paste your code and see the same error you post here :-)

Because this is an entire project, I can't paste the full code. But I found the difference between transformers 3 and 2. Transformers2 maps ID to "[unk]" when dealing with characters like '\n','\r' et.al, but transformers3 discards all such characters when dealing with such cases. Like this:
![image](https://user-images.githubusercontent.com/31853251/90902807-9db0d980-e3ff-11ea-8ebf-4abf3d97b732.png)
Thanks very much!<|||||>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.
