title: change key in OrderedDict without losing order
body: <p>Starting with</p>
  
  <pre><code>OrderedDict([('a', 1), ('c', 3), ('b', 2)])
  </code></pre>
  
  <p>is it possible to end up with</p>
  
  <pre><code>OrderedDict([('a', 1), ('__C__', 3), ('b', 2)])
  </code></pre>
  
  <p>making sure that the <code>'__C__'</code> item is before <code>'b'</code> and after <code>'a'</code> i.e. keeping order?</p>