Binary Trees With Factors LeetCode solution in Python

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class Solution:
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    def numFactoredBinaryTrees(self, nums: List[int]) -> int:
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        nums = set(nums)
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        n = len(nums)
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        @lru_cache(None)
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        def helper(num):
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            trees = 1
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            for factor in nums:
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                if not num % factor and num // factor in nums:
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                    trees += helper(factor) * helper(num // factor)
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            return trees
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        return sum(helper(num) for num in nums) % (10**9 + 7)