title: Python: Argparse with list of lists
body: <p>Minimum verifiable example:</p>
  
  <pre><code>import argparse
  
  parser = argparse.ArgumentParser(description='...')
  parser.add_argument('-f','--file', type=str, nargs='+', help='file list')
  
  args = parser.parse_args()
  
  print(args.sparse[:])
  </code></pre>
  
  <p>And the idea is that I call this as: </p>
  
  <pre><code>python my_script.py -f f1 f2 f3 -f some_other_file1 some_other_file2 ...
  </code></pre>
  
  <p>And the output would be: </p>
  
  <pre><code>[ [ f1 f2 f3 ] [ some_other_file1 some_other_file2 ] ]
  </code></pre>
  
  <p>However, in this case, all that is printed out is: </p>
  
  <pre><code> [ some_other_file1 some_other_file2 ]
  </code></pre>