TensorBoardTracker: wrong arg def

[stas00]

there is a small bug here:

$ python -c "import accelerate.tracking; x = accelerate.tracking.TensorBoardTracker('1')"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/mnt/nvme0/code/huggingface/accelerate-master/src/accelerate/tracking.py", line 155, in __init__
    self.logging_dir = os.path.join(logging_dir, run_name)
  File "/home/stas/anaconda3/envs/py38-pt113/lib/python3.8/posixpath.py", line 76, in join
    a = os.fspath(a)
TypeError: expected str, bytes or os.PathLike object, not NoneType

So the logging_dir arg can't be Optional, which this PR fixes, with it:

$ python -c "import accelerate.tracking; x = accelerate.tracking.TensorBoardTracker('1')"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/mnt/nvme0/code/huggingface/accelerate-master/src/accelerate/tracking.py", line 83, in execute_on_main_process
    return PartialState().on_main_process(function)(self, *args, **kwargs)
TypeError: __init__() missing 1 required positional argument: 'logging_dir'

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[muellerzr]

Thanks for catching!