input: Write a function to merge and sort two lists.
  assert merge_sort([3, 5, 9, 1, 8], [4, 11, 7, 2]) == [1, 2, 3, 4, 5, 7, 8, 9, 11]
  assert merge_sort([0, 3, 4], [1, 2, 5]) == [0, 1, 2, 3, 4, 5]
  assert merge_sort([], [1, 2, 3]) == [1, 2, 3]
output: def merge_sort(list1, list2):
      return sorted(list1 + list2)