title: How would you sort a django mptt tree?
body: <p>Imagine that I have an mptt tree of objects and their population like:</p>
  
  <p>Animal, 60</p>
  
  <ul>
  <li>aardvark, 30   </li>
  <li>bobcat, 20</li>
  <li>chipmunk, 10</li>
  </ul>
  
  <p>Vegetable, 6</p>
  
  <ul>
  <li>apple, 1</li>
  <li>beet, 2</li>
  <li>cauliflower, 3</li>
  </ul>
  
  <p>Mineral 0</p>
  
  <p>How would you sort the above by population on each sublevel?  I want to get to:</p>
  
  <p>Animal, 60</p>
  
  <ul>
  <li>aardvark, 30</li>
  <li>bobcat, 20</li>
  <li>chipmunk, 10</li>
  </ul>
  
  <p>Vegetable, 6</p>
  
  <ul>
  <li>cauliflower, 3</li>
  <li>beet, 2</li>
  <li>apple, 1</li>
  </ul>
  
  <p>Mineral 0</p>
  
  <p>I am building off of mptt in django.</p>