def min_tree(self):
e = sorted(self.e, key=operator.itemgetter(2))
dsu = DSU(self.vertices)
res = WeightedGraph(self.vertices)
for edge in e:
if dsu.find(edge[0]) != dsu.find(edge[1]):
dsu.unite(edge[0], edge[1])
res.add_directed_link(edge[0], edge[1], edge[2])
return res
