How this is different  from backtracking?\n```\n\nclass Solution(object):\n    def subsets(self, nums):\n        self.ans = []\n        \n        self.helper(nums, 0, [])\n        return self.ans\n      \n    def helper(self, nums, index, tmp_arr): \n        self.ans.append(tmp_arr)      \n        for idx in range(index, len(nums)):      \n            self.helper(nums, idx+1,  tmp_arr + [nums[idx]])\n```

How this is different  from backtracking?\n\n\nclass Solution(object):\n    def subsets(self, nums):\n        self.ans = []\n        \n        self.helper(nums,