title: Python - "Unlist" a nested element in a list
body: <p>Is there any quick ways to untangle elements in a list?
  For example:
  Given</p>
  
  <pre><code>list = [[1,2,3],[4,2],2,1,3]
  </code></pre>
  
  <p>We'll have:</p>
  
  <pre><code>list = [1,2,3,4,2,2,1,3]
  </code></pre>