refactor: graph.edges() returns a list in order of addition; both edges() return copies

[petercorke]

Summary

graph.edges() returns a list in order of addition, and both graph.edges() and vertex.edges() return copies. This supersedes #36, which made only the copy half of this change.

What was wrong

BaseGraph.edges() returned the graph's own set of edges, although it was documented as a list (0.6.5 :rtype: list of Edge references). So it had no defined order, and, like BaseVertex.edges(), it handed out the live container: clearing the result emptied the graph's records without updating ne, and removing edges while iterating over vertex.edges() skipped some.

Change

• The graph keeps its edges in a dict[Edge, None] used as an insertion-ordered set (keyed by the edge object, hashed by identity). Removal is still O(1), and the attribute is renamed _edges so it no longer shares a name with the vertex's list.
• graph.edges() is list(self._edges), vertex.edges() is list(self._edgelist); both are new lists.
• Docstrings say which edges are returned for each vertex kind, that an undirected self-loop is listed twice at its vertex (once per end, as for the degree) but once in graph.edges(), and carry a versionchanged note.
• Corrected two stale sentences found on the way: incidence() numbered edges "in the order they appear in graph.edges()" (now well defined) and claimed degree counts outgoing edges only (false since the degree change).

Breaking change (1.0)

graph.edges() is a list, not a set: code that used set operations on the result (|, -, .add()) needs set(g.edges()). Downstream, RTB's PoseGraph and LatticePlanner only iterate it.

Tests

tests/test_edges_list.py (22 tests, both graph kinds): type, order, order surviving removal, both results are copies, removing while iterating on both methods visits every edge, parallel edges, loops, Edge.remove, remove_vertex.

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Up to standards ✅

🟢 Issues 0 issues

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🟢 Metrics 16 complexity · 0 duplication

Metric	Results
Complexity	16
Duplication	0

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[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 94.61%. Comparing base (eb78442) to head (a063fb2).

Files with missing lines	Patch %	Lines
src/pgraph/PGraph.py	90.90%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #43   +/-   ##
=======================================
  Coverage   94.61%   94.61%           
=======================================
  Files           3        3           
  Lines        1208     1208           
=======================================
  Hits         1143     1143           
  Misses         65       65           

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