title: Insert an element at a specific index in a list and return the updated list
body: <p>I have this:</p>
  <pre><code>&gt;&gt;&gt; a = [1, 2, 4]
  &gt;&gt;&gt; print a
  [1, 2, 4]
  
  &gt;&gt;&gt; print a.insert(2, 3)
  None
  
  &gt;&gt;&gt; print a
  [1, 2, 3, 4]
  
  &gt;&gt;&gt; b = a.insert(3, 6)
  &gt;&gt;&gt; print b
  None
  
  &gt;&gt;&gt; print a
  [1, 2, 3, 6, 4]
  </code></pre>
  <p>Is there a way I can get the updated list as the result, instead of updating the original list in place?</p>