Merge Similar Items LeetCode solution in Python

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class Solution:
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    def mergeSimilarItems(
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        self, items1: List[List[int]], items2: List[List[int]]
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    ) -> List[List[int]]:
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        merge_item = items1 + items2
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        d = defaultdict(int)
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        for i in merge_item:
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            value, weight = i
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            d[value] = d[value] + weight
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        result = []
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        for j in sorted(d):
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            result.append([j, d[j]])
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        return result