input: Write a python function to combine and sort two arrays.
  assert combine_sorted_arrays([1, 2, 5], [2, 4, 6]) == [1, 2, 2, 4, 5, 6]
  assert combine_sorted_arrays([3, 1], [4, 2]) == [1, 2, 3, 4]
  assert combine_sorted_arrays([], [0, -1, 3]) == [-1, 0, 3]
output: def combine_sorted_arrays(arr1, arr2):
      return sorted(arr1 + arr2)