title: Group in a group ArgParse
body: <p>So I'm using argparse and I'm trying to create something that I can't seem to find the solution anywhere.</p>
  
  <p>I'm trying to do <code>[A | [B C]]</code>. So either I have <code>A</code> or <code>(B and C)</code>.</p>
  
  <p>EDIT
  So some example of code would be</p>
  
  <pre><code>parser = argparse.ArgumentParser()
  group = parser.add_mutually_exclusive_group(required=False)
  group.add_argument("-a")
  more = group.add_mutually_exclusive_group()
  more.add_argument("-b")
  more.add_argument("c")
  </code></pre>
  
  <p>This however ends up giving me <code>[A | [B | C]]</code></p>