给我一个拓扑排序的代码

Sure, here's a sample code for topological sorting in Python:

from collections import deque

def topological_sort(graph):
    # Create a dictionary to store the in-degrees of each vertex
    in_degree = {node: 0 for node in graph}

    # Calculate the in-degrees of each vertex
    for node in graph:
        for neighbor in graph[node]:
            in_degree[neighbor] += 1

    # Create a queue to store the nodes with zero in-degree
    zero_in_degree_nodes = deque([node for node in in_degree if in_degree[node] == 0])

    # Perform topological sort
    sorted_nodes = []
    while zero_in_degree_nodes:
        node = zero_in_degree_nodes.popleft()
        sorted_nodes.append(node)

        for neighbor in graph[node]:
            in_degree[neighbor] -= 1
            if in_degree[neighbor] == 0:
                zero_in_degree_nodes.append(neighbor)

    # Check for cycles
    if len(sorted_nodes) != len(graph):
        raise ValueError("Graph has a cycle")

    return sorted_nodes

Hope this helps!