Merge Sorted Array In Place

You are given two integer arrays `nums1` and `nums2`, sorted in non-decreasing order. The first array `nums1` has a length of `m + n`, where the first `m` elements are the elements to be merged, and the last `n` elements are set to 0 and should be ignored. The second array `nums2` has a length of `n`. Implement a function `merge(nums1, m, nums2, n)` that merges `nums2` into `nums1` in-place so that the first `m + n` elements of `nums1` contain all elements in sorted non-decreasing order. The function should return the merged `nums1` list (returning the same list object is acceptable). Since the list is modified in-place, the caller can also just inspect `nums1`, but returning the list helps the test harness.

>>> nums1 = [1,2,3,0,0,0]
>>> m = 3
>>> nums2 = [2,5,6]
>>> n = 3
>>> result = merge(nums1, m, nums2, n)
>>> result
[1,2,2,3,5,6]

>>> nums1 = [1]
>>> m = 1
>>> nums2 = []
>>> n = 0
>>> merge(nums1, m, nums2, n)
[1]

>>> nums1 = [0]
>>> m = 0
>>> nums2 = [1]
>>> n = 1
>>> merge(nums1, m, nums2, n)
[1]