Add first priority tests, fix some issues and refactor the code.
Rename v to z.
Add tests for more priorities.
Fix bug in priority 7. Change the test appropriately.
Refactor disjoint neighbor detection into another method for speed.
Remove redundant method.
Rename a variable for readability. Expose a possible bug.
Add tests for single vertex priorities.
Fix a bug for priority 10. Finish tests for priorities.
Remove redundant comment.
Add a test for the bug in shared neighbor's neighbor detection.
Fix the bug with shared neighbors' neighbors.