GPT2 tokenizer decode swallows space
### System Info

- `transformers` version: 4.25.1
- Platform: Linux-5.15.0-56-generic-x86_64-with-glibc2.35
- Python version: 3.9.15
- Huggingface_hub version: 0.11.1
- PyTorch version (GPU?): 1.10.2+cu113 (True)
- Tensorflow version (GPU?): not installed (NA)
- Flax version (CPU?/GPU?/TPU?): 0.4.1 (cpu)
- Jax version: 0.4.1
- JaxLib version: 0.4.1
- Using GPU in script?: no
- Using distributed or parallel set-up in script?: no


### Who can help?

@ArthurZucker 

### Information

- [ ] The official example scripts
- [X] My own modified scripts

### Tasks

- [ ] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...)
- [X] My own task or dataset (give details below)

### Reproduction

```python
from transformers import AutoTokenizer

tokenizer = AutoTokenizer.from_pretrained("gpt2")
tokens = tokenizer.encode("y is ?")
print(tokens)  # prints [88, 318, 5633]
print(tokenizer.decode(tokens))  # prints "y is?" (wrong!)
```

### Expected behavior

It should roundtrip back to the same string, matching the behavior of OpenAI's reference implementation: https://github.com/openai/gpt-2/blob/master/src/encoder.py

OpenAI's implementation encodes to the same tokens, but correctly decodes them to `"y is ?"`
Hi, @daniel-ziegler use `clean_up_tokenization_spaces=False` in `decode` so the code will be - 
`print(tokenizer.decode(tokens, clean_up_tokenization_spaces=False))` 
this solves the problem,

thanks, 
susnato.<|||||>Indeed! Thanks for jumping this quickly @susnato 🤗<|||||>Thanks, that does work. I still think it's a bug that that isn't the default behavior for reversible tokenizers like GPT2's -- there's only one standard decoding behavior for them and it should be the default.<|||||>@daniel-ziegler, I think it's due to the reason that most tokenizers don't preserve the structure such as spaces, and the huggingface team didn't want to have different implementations for both type of tokenizers (which will make the code more complecated!), so it's True by default.