fixed doctest on multigraph

Author: Saatvik Rao

src/sage/graphs/generic_graph.py

@@ -15815,7 +15815,7 @@ def power(self, k):
 
         Testing on graph with multiple edges::
 
-            sage: G = DiGraph([(0, 1), (0, 1), (1, 2), (2, 3), (3, 0), (2, 4), (4, 5)])
+            sage: G = DiGraph([(0, 1), (0, 1), (1, 2), (2, 3), (3, 0), (2, 4), (4, 5)], multiedges=True)
             sage: PG = G.power(3)
             sage: PG.edges(sort=True, labels=False)
             [(0, 1), (0, 2), (0, 3), (0, 4), (1, 0), (1, 2), (1, 3), (1, 4), (1, 5), (2, 0), (2, 1), (2, 3), (2, 4), (2, 5), (3, 0), (3, 1), (3, 2), (4, 5)]