v0.1.3

[IvanChernyshov]

• Added:

  • undirected_edges_unique(...) for undirected containers and use it internally for component generator extraction.
  • Read-only accessors PeriodicComponent.snf and PeriodicComponent.tree_parent_map() and updated canonical_lift(...) to avoid touching private component caches.

• Changed:

  • LiftPatch.to_networkx(as_undirected=True, ...) now stores direction and orig-edge snapshots under a single reserved edge attribute __pbcgraph__ to avoid collisions with user attributes.
  • Minor: code that previously read _pbc_* or orig_edges from NetworkX exports must now read __pbcgraph__.

• Performance:

  • lift_patch(...) avoids redundant incoming-edge traversal for undirected containers (no semantic change).
  • Refactored edges(), neighbors(), and in_neighbors() to use streaming deterministic iteration (avoid building a full edge list just to sort it).

• Refactored:

  • Refactored LiftPatch.to_networkx(...) into small helpers (no behavior change).
  • Split pbcgraph.alg.lift into _lift_patch and _canonical_lift implementation modules, keeping the public API unchanged.
  • General refactors: introduce an internal constant PBC_META_KEY for NetworkX export metadata, simplify internal key filtering in undirected containers, and apply small style cleanups.