Is Graph Bipartite? LeetCode solution in Python

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class Solution:
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    def isBipartite(self, graph: List[List[int]]) -> bool:
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        v = len(graph)
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        color = [-1] * v
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        color[0] = 1
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        def helper(src, q):
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            q.append(src)
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            while q:
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                node = q.pop(0)
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                for j in graph[node]:
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                    if color[j] == -1:
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                        color[j] = 1 - color[node]
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                        q.append(j)
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                    elif color[node] == color[j]:
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                        return False
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            return True
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        for i in range(v):
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            if not helper(i, []):
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                return False
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        return True