input: Write a function that merges two lists of integers into one sorted list without using the in-built sort function. 
  
  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([], [4, 11, 7, 2]) == [2, 4, 7, 11]
  assert merge_sort([3, 5, 9, 1, 8], []) == [1, 3, 5, 8, 9]
  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