fix: add special edge handling in bfs, dfs and base partitioner

[CHERRY-ui8]

This PR enhances the robustness and correctness of the graph partitioning logic by introducing validation and filtering for edges.

[gemini-code-assist]

Summary of Changes

Hello @CHERRY-ui8, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the robustness and correctness of the graph partitioning logic by introducing comprehensive validation and filtering for edges. It addresses potential issues arising from malformed or self-looping edges within the base partitioner's batch conversion and the BFS and DFS algorithms, ensuring that the generated graph communities are based on valid and well-formed edge structures.

Highlights

• Robust Edge Handling: Implemented explicit checks to filter out invalid edge formats and self-loops within the community2batch function in base_partitioner.py, ensuring only valid edges are processed.
• Standardized Edge Representation: Updated the BFS and DFS partitioners to use frozenset[str] for internal edge storage (comm_e), promoting consistency and proper handling of undirected edges.
• Pre-Community Edge Validation: Added a final validation step in both BFS and DFS partitioners to ensure that only valid, two-node frozenset edges are converted to tuples and included when constructing the Community object.

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[gemini-code-assist]

Code Review

This pull request introduces more robust handling for edges, particularly self-loops and malformed edge data, across the base partitioner, BFS partitioner, and DFS partitioner. The changes correctly use frozenset for undirected edges and filter them before creating communities, which prevents potential errors. I've identified one area for improvement related to code duplication between the BFS and DFS partitioners, which could be refactored for better maintainability.

[gemini-code-assist]

This logic for filtering out invalid edges is duplicated in graphgen/models/partitioner/dfs_partitioner.py (lines 76-79). To improve maintainability and adhere to the DRY (Don't Repeat Yourself) principle, consider extracting this list comprehension into a common helper function. Since both BFSPartitioner and DFSPartitioner inherit from BasePartitioner, a static or protected helper method in the base class would be a suitable location.