Add method: has_node

[haoxins]

• I ran rustfmt locally
• I have added the tests to cover my changes.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.

[CLAassistant]

All committers have signed the CLA.

[mtreinish]

Thanks for doing this, overall this is a nice addition! I left a small inline comment to simplify the code slightly. But besides that could you add a unit test that validates the case when this new method returns false? This also is missing the type annotation stubs and it'll fail the ci job checking those. The process for adding them is documented here: https://github.com/Qiskit/rustworkx/blob/main/CONTRIBUTING.md#type-annotations

Also if you don't mind could you add a release note to document the new API. The process for doing this is documented here: https://github.com/Qiskit/rustworkx/blob/main/CONTRIBUTING.md#release-notes

[coveralls]

Pull Request Test Coverage Report for Build 8822336562

Details

• 8 of 8 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.002%) to 96.496%

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Totals
Change from base Build 8821112146:	0.002%
Covered Lines:	17322
Relevant Lines:	17951

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💛 - Coveralls

[mtreinish]

Thanks for the quick update! This looks ready to go to me now, the only thing I think missing is test coverage for PyGraph. Once that's there I think this is good to merge.

[IvanIsCoding]

LGTM, thanks for adding the tests