[JoostvanDijkTenneT]

Checklist

Please check if the PR fulfills these requirements:

• [ Yes] PR Title follows conventional commit messages
• [ Yes] Tests for the changes have been added (for bug fixes / features)
• [ Not relevant] Docs have been added / updated (for bug fixes / features)
• [ Yes] All commits in this PR are DCO signed-off (see CONTRIBUTING.md)

Does this PR already have an issue describing the problem?

No.

Fixes

Parallel branches which would cause two connected components when removed from the graph are now marked as a bridge. This PR fixes that.

Does this PR introduce a breaking change?

• [ ] Yes
• [ X] No

[Copilot]

🟡 Changes recommended

The obsolete sparse import and number_edges assignment trigger Ruff F401/F841 violations in CI pre-commit checks and must be removed.

1 open issue

• Remove unused sparse import and number_edges assignment · New

What changed in this PR

This PR corrects bridge detection during network preprocessing so parallel branches are not incorrectly treated as individual bridges.

Changes:

• Uses a NetworkX MultiGraph to preserve parallel edges.
• Adds a regression test for two parallel branches.
• Cleans up LODF tests and relaxes the voltage-angle comparison tolerance.

File	Description
tests/​preprocess/​test_helper_functions.py	Adds regression coverage for parallel branches.
tests/​numpy/​test_lodf.py	Removes unused variables, corrects spelling, and adjusts angle tolerance.
src/​dc_plus/​preprocess/​helper_functions.py	Replaces sparse-matrix graph construction with a multigraph.

_{Review effort: Balanced}