Number of Good Ways to Split a String LeetCode solution in Python

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class Solution:
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    def numSplits(self, s: str) -> int:
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        one = set()
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        two = set()
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        dic = {}
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        for i in s:
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            dic[i] = dic.get(i, 0) + 1
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            two.add(i)
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        tot = 0
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        for i in s:
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            one.add(i)
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            dic[i] -= 1
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            if dic[i] == 0:
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                two.remove(i)
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            if len(one) == len(two):
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                tot += 1
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        return tot