v0.1.3

This release merges three versions (0.1.1 => 0.1.3) and is focused on making pbcgraph deterministic, safer to mutate, and more robust for lift-based workflows.

• Deterministic, stable core iteration

  • All public iteration APIs (nodes, edges, neighbors, successors, predecessors, plus in_neighbors*) now yield results deterministically, with a stable fallback order when objects are not mutually comparable.
  • Iteration internals were further optimized in 0.1.3 to stream deterministically without materializing/sorting full edge lists.

• Safer attribute handling and edge-key semantics

  • Node/edge data accessors now return read-only live views; attribute mutation is routed through set_node_attrs() / set_edge_attrs() (with clarified data_version semantics).
  • Edge key generation became deterministic and local to (u, v) pairs; explicit keys must be int (bool rejected).
  • PeriodicGraph.check_invariants() was added to validate undirected pairing invariants.

• Finite lift patches and NetworkX export

  • Introduced lift_patch(...) to extract finite patches of the infinite lift around a seed instance (BFS radius and/or cell-index bounding boxes), storing snapshot edge attributes and deterministically deduplicating paired realizations for undirected containers.
  • Directed periodic containers now produce directed patches by default; LiftPatch.to_networkx(as_undirected=True, ...) provides undirected views.
  • 0.1.3 change: NetworkX export metadata for undirected views is consolidated under a single reserved edge attribute __pbcgraph__ (and PBC_META_KEY internally). Code that previously read _pbc_* or orig_edges must now read __pbcgraph__.

• Canonical lifts

  • Added canonical_lift(...) to select strand representatives (cosets in Z^d/L), with placements tree, best_anchor, and greedy_cut, and optional spanning-tree edge return.
  • Added read-only PeriodicComponent.snf and PeriodicComponent.tree_parent_map() and adjusted canonical lift internals to avoid touching private component caches.

• Robustness and maintenance

  • Added scoped errors: CanonicalLiftError, LiftPatchError.
  • Removed SymPy by implementing exact inversion for unimodular matrices.
  • Refactoring work split pbcgraph.alg.lift into _lift_patch / _canonical_lift modules and simplified internal filtering/exports; lift_patch(...) for undirected containers avoids redundant incoming-edge traversal (no semantic change).