updated is_brace()

Author: janmenjayap

src/sage/graphs/matching_covered_graph.py

@@ -2643,13 +2643,13 @@ def is_brace(self, coNP_certificate=False):
             True
             sage: H = graphs.CompleteBipartiteGraph(3, 3)
             sage: H.delete_edge(0, 3)
-            sage: G = MatchingCoveredGraph(G)
+            sage: G = MatchingCoveredGraph(H)
             sage: G.is_brace(coNP_certificate=True)
             (False,
-             [(1, 2, None), (1, 4, None), (3, 4, None)],
-             {0, 1, 3},
+             [(4, 1, None), (5, 1, None), (4, 2, None), (5, 2, None)],
+             {0, 4, 5},
              'nontrivial barrier cut',
-             {2, 4})
+             {1, 2})
 
         If the input matching covered graph is nonbipartite, a
         :exc:`ValueError` is thrown::