N-ary Tree Postorder Traversal LeetCode solution in Python

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class Solution(object):
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    def postorder(self, root):
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        """
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        :type root: Node
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        :rtype: List[int]
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        """
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        res = []
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        def bfs(root):
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            if root:
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                for child in root.children:
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                    bfs(child)
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                res.append(root.val)
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        bfs(root)
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        return res