title: A list of string into a nested list of string
body: <p>so I need to turn a list of str into a list of list of str.</p>
  
  <p>EX:</p>
  
  <pre><code>thing = [' a b c', 'e f g']
  </code></pre>
  
  <p>into:</p>
  
  <pre><code>[['a', 'b', 'c'], ['e', 'f', 'g']]
  </code></pre>
  
  <p>My code keeps returning a mistake:</p>
  
  <pre><code>coolthing = []   
  abc = []
  for line in thing:
      abc = coolthing.append(line.split())
  return abc
  </code></pre>