docs: add pydoc for llm/ (#110)

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# Summary
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## Pre-Review Checklist

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Ensure that the following pass:

- [ ] `make format && make lint` or via prek validation.
- [ ] `make test` passes locally
- [ ] `make test-e2e` passes locally
- [ ] `make test-ci-container` passes locally (recommended)

## Pre-Merge Checklist

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- [ ] New or updated tests for any fix or new behavior
- [ ] Updated documentation for new features and behaviors, including
docstrings for API docs.

## Other Notes

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- Closes #<issue>

---------

Signed-off-by: Sean Yang <seayang@nvidia.com>
Signed-off-by: seayang-nv <seayang@nvidia.com>
Co-authored-by: Kendrick Boyd <kendrickb@nvidia.com>

Author: seayang-nv