input: Write a function to merge two lists of integers into one sorted list without using the in-built sort function. If the function is given empty lists, it should return an empty list.
  
  def merge_sort(list1, list2):
      merged_list = list1 + list2
      for i in range(len(merged_list)):
          min_idx = i
          for j in range(i+1, len(merged_list)):
              if merged_list[min_idx] > merged_list[j]:
                  min_idx = j
          merged_list[i], merged_list[min_idx] = merged_list[min_idx], merged_list[i]
      return merged_list
  
  assert merge_sort([3, 5, 9, 1, 8], [4, 11, 7, 2]) == [1, 2, 3, 4, 5, 7, 8, 9, 11]
  assert merge_sort([10, 5, 8], [1, 3, 7]) == [1, 3, 5, 7, 8, 10]
  assert merge_sort([], [4, 2, 5]) == [2, 4, 5]
  assert merge_sort([6, 7], []) == [6, 7]
  assert merge_sort([], []) == []
output: def merge_sort(list1, list2):
      merged_list = list1 + list2
      for i in range(len(merged_list)):
          min_idx = i
          for j in range(i+1, len(merged_list)):
              if merged_list[min_idx] > merged_list[j]:
                  min_idx = j
          merged_list[i], merged_list[min_idx] = merged_list[min_idx], merged_list[i]
      return merged_list