title: Python syntax for namedtuple inside a namedtuple
body: <p>Is it possible to have a <code>namedtuple</code> inside another <code>namedtuple</code>? </p>
  
  <p>For example:</p>
  
  <pre><code>from collections import namedtuple
  
  Position = namedtuple('Position', 'x y')
  Token = namedtuple('Token', ['key', 'value', Position])
  </code></pre>
  
  <p>which gives a <em>"ValueError: Type names and field names must be valid identifiers"</em></p>
  
  <p>Also, I am curious if there is a more <em>Pythonic approach</em> to build such a nested container?</p>