* Use single-arg form for `#[pymodule]` functions in docs and tests
* Update guide/src/function.md
Co-authored-by: Icxolu <10486322+Icxolu@users.noreply.github.com>
* Add test of two-argument module function
* Fix new test
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Co-authored-by: Icxolu <10486322+Icxolu@users.noreply.github.com>