Fixing dataset directory path and tensorflow 2.0 fit module

[sablevinayak]

Existing code had a issue for dataset directory and also the current version of tensorflow 2.0 deprecated fit_generator and introduced fit method for the same functionality.

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[MarkDaoust]

Thanks for the PR. That fixes the notebook, but we can't merge this until you sign the CLA.

[sablevinayak]

@MarkDaoust Thanks for the review. The CLA check has been completed now.