title: Repeat the very first and last items while doing islice?
body: <p>In the following list of items I want to access two consecutive list items at once and also access the index. On top of that for the very first and last item of the list I want to repeat the data. </p>
  
  <pre><code>my_list = ['A','C','G','T','T','C','G','A','G']
  
  print(my_list)
  print()
  
  
  for (n1, v1), (n2,v2) in zip(enumerate(my_list), itertools.islice(enumerate(my_list), 1, None)):
          print(v1)
          print(v2)
          print()
  
  # gives me
  
  ['A', 'C', 'G', 'T', 'T', 'C', 'G', 'A', 'G']
  
  (0, 'A')
  (1, 'C')
  
  (1, 'C')
  (2, 'G')
  
  (2, 'G')
  (3, 'T')
  
  (3, 'T')
  (4, 'T')
  
  (4, 'T')
  (5, 'C')
  
  (5, 'C')
  (6, 'G')
  
  (6, 'G')
  (7, 'A')
  
  (7, 'A')
  (8, 'G')
  </code></pre>
  
  <p>How, do I repeat the same index only for very first and very last items??</p>
  
  <p>Expected output:</p>
  
  <pre><code>(0, 'A')
  (0, 'A')
  
  (0, 'A')
  (1, 'C')
  
  (1, 'C')
  (2, 'G')
  
  .....
  .....
  
  (8, 'G')
  (8, 'G')
  </code></pre>