Fix tests with networkx 2.7

[antonio-rojas]

The output of matching displays edges in reverse order in 2.7, which break tests. To fix it, we make the output of matching and Edgesview, which also fixes some other issues, such as:

sage: G=graphs.CompleteGraph(4)
sage: m=G.matching(); m
[(1, 2, None), (0, 3, None)]
sage: (3, 0, None) in m
False

Also, networkx.node_clique_number now outputs a collections.defaultdict object, so we explicitly cast it to dict for backwards compatibility.

CC: @mkoeppe @kiwifb @tornaria

Component: graph theory

Author: Antonio Rojas

Branch/Commit: 8452003

Reviewer: David Coudert

Issue created by migration from https://trac.sagemath.org/ticket/33495

[antonio-rojas]

Branch: u/arojas/fix_tests_with_networkx_2_7

[antonio-rojas]

Commit: 66a1fe8

[antonio-rojas]

Author: Antonio Rojas

[antonio-rojas]

New commits:

c6dc11b	Use EdgesView for matching output
66a1fe8	Cast networkx.node_clique_number output to dict

[dcoudert]

comment:4

You should

• specify the input format to Graph to reduce the overhead of building the graph before returning the result.

-                return EdgesView(Graph([(u, v, L[frozenset((u, v))]) for u, v in d]))
+                return EdgesView(Graph([(u, v, L[frozenset((u, v))]) for u, v in d], format='list_of_edges'))

• update the documentation to clarify that the output is now a EdgesView
• modify a doctest to show that the result is of type EdgesView, for instance like

-            sage: sorted(g.matching(use_edge_labels=True))
-            [(0, 3, 3), (1, 2, 6)]
+            sage: m = g.matching(use_edge_labels=True)
+            sage: type(m)
+            <class 'sage.graphs.views.EdgesView'>
+            sage: sorted(m)
+            [(0, 3, 3), (1, 2, 6)]

[sagetrac-git]

Changed commit from 66a1fe8 to 8452003

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

2a7fa3c	Specify the input format to Graph
8452003	Update tests and docs

[antonio-rojas]

comment:6

Done, thanks

[dcoudert]

comment:7

LGTM.

[dcoudert]

Reviewer: David Coudert

[mkoeppe]

comment:8

Follow-up: #33520

[vbraun]

Changed branch from u/arojas/fix_tests_with_networkx_2_7 to 8452003