Find Eventual Safe States LeetCode solution in Python

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import collections
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class Solution:
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    def eventualSafeNodes(self, graph: list[list[int]]) -> list[int]:
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        n = len(graph)
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        ans = []
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        for i in range(n):
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            if not graph[i]:
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                ans.append(i)
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        def loop(key, loops):
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            loops.append(key)
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            for i in graph[key]:
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                if i in loops:
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                    return False
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                elif i in ans:
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                    continue
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                else:
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                    r = loop(i, loops)
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                    if r == True:
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                        continue
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                    else:
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                        return False
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            idx = loops.index(key)
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            loops.pop(idx)
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            return True
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        for i in range(n):
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            loops = []
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            if i in ans:
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                continue
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            r = loop(i, loops)
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            if r == True:
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                ans.append(i)
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        return sorted(ans)