Replace tuple with Iterable[torch.Tensor]

[dxoigmn]

What does this PR do?

We had type annotations for tuple everywhere, but this is not great because it doesn't tell us what is inside of the tuple. As such, I changed it to Iterable[torch.Tensor]. I also tried to cleanup the dispatch code in all places. This PR, however, does not support input dictionaries right now. I think the "modality dispatch" abstraction in #115 should be pulled out and rebased on this PR.

Type of change

Please check all relevant options.

• Improvement (non-breaking)
• Bug fix (non-breaking)
• New feature (non-breaking)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Testing

Please describe the tests that you ran to verify your changes. Consider listing any relevant details of your test configuration.

• make test

Before submitting

• The title is self-explanatory and the description concisely explains the PR
• My PR does only one thing, instead of bundling different changes together
• I list all the breaking changes introduced by this pull request
• I have commented my code
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have run pre-commit hooks with pre-commit run -a command without errors

Did you have fun?

Make sure you had fun coding 🙃

[mzweilin]

LGTM