title: Django get the max PK
body: <p>I am trying to recieve the max PK using django ORM.
  By max I mean I want to do this query:</p>
  
  <pre><code>SELECT MAX(pk_column)
  FROM   some_table;
  </code></pre>
  
  <p>the thing is that I want something like <code>some_table_model.max(pk)</code> , it is important for me that the Django will translate it to the query above so it will use indexs. So:</p>
  
  <ol>
  <li>Is there something like that build in?</li>
  <li>Is there a way to write a generic function without doing it for a specific model?</li>
  </ol>
  
  <p>Thank you in advance.</p>