input: def insertion_sort(arr):
      for i in range(1, len(arr)): 
    
          key = arr[i] 
    
          # Move elements of arr[0..i-1], 
          # that are greater than key, 
          # to one position ahead of 
          # their current position 
          j = i-1
          while j >= 0 and key < arr[j] : 
                  arr[j + 1] = arr[j] 
                  j -= 1
          arr[j + 1] = key
      return arr
  
  """
  Sort a list of n distinct integers using insertion sort.
  
  >>> insertion_sort([4, 3, 2, 10, 12, 1, 5, 6])
  [1, 2, 3, 4, 5, 6, 10, 12]
  >>> insertion_sort([9, 7, 8, 6, 4, 5, 3, 1, 2])
  [1, 2, 3, 4, 5, 6, 7, 8, 9]
  """
output:     for i in range(1, len(arr)): 
          key = arr[i] 
          j = i-1
          while j >= 0 and key < arr[j] : 
                  arr[j + 1] = arr[j] 
                  j -= 1
          arr[j + 1] = key
      return arr