* refactor: extract method from class to new func
* test: add new tests
* refactor: simplify funcs to improve readability
* refactor: extract new func from larger func
* refactor: remove recursion from func
* refactor: remove coupling with graph and vertex
* refactor: create adapter funcs to use new code
* refactor: add test for sorting up to vertex N with is_start=True
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Co-authored-by: Gabriel Luiz Freitas Almeida <gabriel@langflow.org>
