4Sum LeetCode solution in Python

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class Solution:
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    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
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        if len(nums) < 4:
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            return []
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        nums.sort()
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        res = []
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        for i in range(len(nums)):
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            for j in range(i + 1, len(nums)):
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                l = j + 1
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                r = len(nums) - 1
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                while l < r:
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                    sum_ = nums[i] + nums[j] + nums[l] + nums[r]
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                    a = [nums[i], nums[j], nums[l], nums[r]]
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                    if sum_ == target and a not in res:
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                        res.append(a)
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                    if sum_ > target:
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                        r -= 1
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                    else:
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                        l += 1
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                        while l < r and nums[l - 1] == nums[l]:
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                            l += 1
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        return res
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        # An Upvote will be encouraging