input: 
  def merge_sort(list1: List[int], list2: List[int]) -> List[int]:
      """Merge two lists of integers into one sorted list without using the built-in sort function.
      >>> merge_sort([3, 5, 9, 1, 8], [4, 11, 7, 2])
      [1, 2, 3, 4, 5, 7, 8, 9, 11]
      """
  
output:     result = []
      i, j = 0, 0
      while i < len(list1) and j < len(list2):
          if list1[i] < list2[j]:
              result.append(list1[i])
              i += 1
          else:
              result.append(list2[j])
              j += 1
      result.extend(list1[i:])
      result.extend(list2[j:])
      return result