input: def insertion_sort(arr):
      """ Sort a list of n distinct integers using the insertion sort algorithm.
      >>> insertion_sort([12, 11, 13, 5, 6])
      [5, 6, 11, 12, 13]
      >>> insertion_sort([31, 41, 59, 26, 41, 58])
      [26, 31, 41, 41, 58, 59]
      """
      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
output:     return arr