如何修复有向图，使最顶层的父级始终是第一级？

from collections import defaultdict, deque

class Graph:
    def __init__(self, vertices):
        self.graph = defaultdict(list)
        self.V = vertices

    def add_edge(self, u, v):
        self.graph[u].append(v)

    def topological_sort(self):
        in_degree = [0] * self.V
        for i in self.graph:
            for j in self.graph[i]:
                in_degree[j] += 1

        queue = deque()
        for i in range(self.V):
            if in_degree[i] == 0:
                queue.append(i)

        topo_order = []
        while queue:
            u = queue.popleft()
            topo_order.append(u)
            for i in self.graph[u]:
                in_degree[i] -= 1
                if in_degree[i] == 0:
                    queue.append(i)

        return topo_order

    def fix_graph(self):
        topo_order = self.topological_sort()
        # Reconstruct the graph based on the topological order
        new_graph = {i: [] for i in range(self.V)}
        for i in topo_order:
            for j in self.graph[i]:
                new_graph[i].append(j)
        self.graph = new_graph
        return topo_order

# Example usage
g = Graph(6)
g.add_edge(5, 2)
g.add_edge(5, 0)
g.add_edge(4, 0)
g.add_edge(4, 1)
g.add_edge(2, 3)
g.add_edge(3, 1)

print("Original graph:", g.graph)
fixed_order = g.fix_graph()
print("Fixed topological order:", fixed_order)
print("Fixed graph:", g.graph)