title: Finding every nth element in a list
body: <p>How can I find every nth element of a list?</p>
  
  <p>For a list <code>[1,2,3,4,5,6]</code>, <code>returnNth(l,2)</code> should return <code>[1,3,5]</code> and for a list <code>["dog", "cat", 3, "hamster", True]</code>, <code>returnNth(u,2)</code> should return <code>['dog', 3, True]</code>. How can I do this?</p>