Update integrations.py
Author: max-yue
Pull request: yes

  File "/share/apps/anaconda3/envs/my_env/lib/python3.7/site-packages/transformers/integrations.py", line 419, in __init__
    self._SummaryWriter = SummaryWriter
UnboundLocalError: local variable 'SummaryWriter' referenced before assignment

# What does this PR do?

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Fixes # (issue)


## Before submitting
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