max_target length for question answering system
Please could you tell the max target length for question answering systems?

I was trying and it does not work if the target length is more than 47 

this is the   [notebook](https://colab.research.google.com/drive/1JzsuPb68L-G4nsMXu57XkwbmzAVrizSS?usp=sharing)
This doesn't seem to be related to your length, but rather to this:

```py
data['labels'].squeeze():  60
---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-12-33cc96af719d> in <module>()
      2   input = tokenizer.decode(data['input_ids'].squeeze(), skip_special_tokens=True)
      3   print("data['labels'].squeeze(): ", len(data['labels'].squeeze()))
----> 4   label = tokenizer.decode(data['labels'].squeeze(), skip_special_tokens=True)
      5   print("data keys: ", data.keys(),"\n")
      6   lines = textwrap.wrap("Query:\n%s\n" % data['question'], width=150)

5 frames
/usr/local/lib/python3.6/dist-packages/sentencepiece/__init__.py in _func(v, n)
    492   def _func(v, n):
    493     if type(n) is int and (n < 0 or n >= v.piece_size()):
--> 494       raise IndexError('piece id is out of range.')
    495     return func(v, n)
    496 

IndexError: piece id is out of range.
```

Your tokenizer doesn't manage to decode your label.<|||||>@LysandreJik  yes understand that buy I did not understand what I did wrong first. Then I realized that labels that are -100 should be 0 again.

Anyway good to figure out late than not doing that