python中拓扑排序如何使用？

paths = [[], [2, 4], [3, 4], [5], [3, 5], []]

indegree = [0 for _ in range(6)]

for u in range(6):

    for v in paths[u]:

        indegree[v] += 1

topological = set()

for i in range(5):

    for u in range(1, 6):

        if u not in topological and indegree[u] == 0:

            topological.add(u)

            for v in paths[u]:

                indegree[v] -= 1

print(topological)