Finding Pairs With a Certain Sum LeetCode solution in Python

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class FindSumPairs:
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    def __init__(self, nums1: List[int], nums2: List[int]):
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        self.nums1 = sorted(nums1)
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        self.nums2 = nums2
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        self.hash2 = defaultdict(int)
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        for n in nums2:
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            self.hash2[n] += 1
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    def add(self, index: int, val: int) -> None:
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        self.hash2[self.nums2[index]] -= 1
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        self.nums2[index] += val
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        self.hash2[self.nums2[index]] += 1
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    def count(self, tot: int) -> int:
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        result = 0
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        for n in self.nums1:
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            if n >= tot:
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                break
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            result += self.hash2[tot - n]
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        return result