Question about whitespace filtering in squad data processor 
Usually to detect for whitespaces in python, the `isspace()` built-in is used. But I noticed for the squad data processor, this is used instead


```
def _is_whitespace(c):
    if c == " " or c == "\t" or c == "\r" or c == "\n" or ord(c) == 0x202F:
        return True
    return False
```

https://github.com/huggingface/transformers/blob/master/src/transformers/data/processors/squad.py#L80

Is there any reason why this is used instead? My guess would be to deal with strings that were processed outside of python. 
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