added save_directories for _psave_pretrained_pt and _tf, changed model to tf_model and pt_model, enable the notebook to run cleanly from top to bottom without error
Author: cfregly
Pull request: yes

@LysandreJik @philschmid 

# What does this PR do?

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Fixes # (issue)


## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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Models:

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Library:

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- pipelines: @LysandreJik

Documentation: @sgugger

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