BAT update: fix type, upload checkpoint; finish inference code; add d…

[zszheng147]

…emo code for inference

What does this PR do?

Fixes # (issue)

Feature/Issue validation/testing

Please describe the tests that you ran to verify your changes and relevant result summary. Provide instructions so it can be reproduced. Please also list any relevant details for your test configuration.

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• [ ] Test B Logs for Test B

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• [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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