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
  
  """
  Example:
  >>> insertion_sort([3, 1, 2, 5, 4])
  [1, 2, 3, 4, 5]
  >>> insertion_sort([10, 9, 8, 7, 6])
  [6, 7, 8, 9, 10]
  """
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