title: how can I filter on the second element in a tuple of tuples?
body: <p>In my model I have a field:</p>
  
  <pre><code>   country = models.CharField(_('Country'), max_length=2, choices=COUNTRIES)
  </code></pre>
  
  <p>Where COUNTRIES is a tuple of tuples like this:</p>
  
  <pre><code>COUNTRIES = (
      ('AF', _('Afghanistan')),
  </code></pre>
  
  <p>... and so on</p>
  
  <p>Now I want to filter an instance of that model, by the country name.</p>
  
  <p>This:</p>
  
  <pre><code>   i = MyModel.objects.filter(country__iexact=query)
  </code></pre>
  
  <p>only lets me filter by the country code.</p>
  
  <p>How can I filter by country name?</p>