title: Remove the outer list of a double list
body: <p>Let's say i have a list that consist of:</p>
  
  <pre><code>[['a','b','c','d']]
  </code></pre>
  
  <p>Is there an easy way to remove the outer list so the output would be</p>
  
  <pre><code>['a','b','c','d']
  </code></pre>
  
  <p>I figured something like pop, but that remove the element, and i just want to remove the outer list.</p>
  
  <p>I know i could iterate over the double list and append the elements to a new list, and the problem would be solved, but im not happy with that solution, i want a smoother one with cleaner code.</p>