title: ArgumentParser for numpy array
body: <p>Is there a way to add an argument to ArgumentParser for an np.array instead of a list?
  I know I can do something like this</p>
  
  <pre><code>import argparse
  parser = argparse.ArgumentParser(prog='PROG')
  parser.add_argument('-foo', action='store', type=int, nargs='+')
  args = parser.parse_args(['-foo', '1', '2'])
  args.foo = np.array(args.foo)
  </code></pre>
  
  <p>But I would like to specify the complete description of the arguments before parsing.</p>
  
  <p>Is there a way to do this?</p>