Given a collection of numbers, nums, that might contain duplicates, return all possible unique permutations in any order.

  Example 1:

Input: nums = [1,1,2] Output: [[1,1,2], [1,2,1], [2,1,1]]

Example 2:

Input: nums = [1,2,3] Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

  Constraints:

1 <= nums.length <= 8
-10 <= nums[i] <= 10