cannot import name AddedToken
# 🐛 Bug

## Information

Model I am using (Bert, XLNet ...): Albert

Language I am using the model on (English, Chinese ...): English

     27 from typing import List, Optional, Sequence, Tuple, Union
     28 
---> 29 from tokenizers import AddedToken, Encoding
     30 from tokenizers.decoders import Decoder
     31 from tokenizers.implementations import BaseTokenizer

ImportError: cannot import name 'AddedToken'


The problem arises when using:
* [ ] the official example scripts: (give details below)
* [ ] my own modified scripts: (give details below)


The tasks I am working on is:
* [ ] an official GLUE/SQUaD task: (give the name): 
* [ ] my own task or dataset: (give details below)

## To reproduce

Steps to reproduce the behavior:

1.
2.
3.

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## Expected behavior

<!-- A clear and concise description of what you would expect to happen. -->

## Environment info
<!-- You can run the command `python transformers-cli env` and copy-and-paste its output below.
     Don't forget to fill out the missing fields in that output! -->
     
- `transformers` version:
- Platform:
- Python version:
- PyTorch version (GPU?):
- Tensorflow version (GPU?):
- Using GPU in script?:
- Using distributed or parallel set-up in script?:

Created another environment from scratch and it got resolved.<|||||>you need install transformers this way:

```
git clone https://github.com/huggingface/transformers
cd transformers
pip install .
```<|||||>> you need install transformers this way:
> 
> ```
> git clone https://github.com/huggingface/transformers
> cd transformers
> pip install .
> ```

This worked for me thanks!<|||||>> you need install transformers this way:
> 
> ```
> git clone https://github.com/huggingface/transformers
> cd transformers
> pip install .
> ```

I was having a similar issue on colab:
```
can't pickle AddedToken objects
```
This solution also worked for me. Thanks!<|||||>> you need install transformers this way:
> 
> ```
> git clone https://github.com/huggingface/transformers
> cd transformers
> pip install .
> ```

Thanks much, this worked for me!<|||||>> you need install transformers this way:
> 
> ```
> git clone https://github.com/huggingface/transformers
> cd transformers
> pip install .
> ```

This solution doesn't work for me! I don't know maybe there is a conflict with `pip` an `conda`. I guess after I installed a package `bert_score` by conda, this error appeared and won't go