code: def make_undirected(self):
          "Make a digraph into an undirected graph by adding symmetric edges."
          for a in self.dict.keys():
              for (b, distance) in self.dict[a].items():
                  self.connect1(b, a, distancef make_undirected(self):
          "Make a digraph into an undirected graph by adding symmetric edges."
          for a in self.dict.keys():
              for (b, distance) in self.dict[a].items():
                  self.connect1(b, a, distance)
docs: Make a digraph into an undirected graph by adding symmetric edges.