title: Django making a list of a field grouping by another field in model
body: <p>I have a model called MyModel which has some dummy data as follows:</p>
  
  <pre><code>     item    date     value
  ------------------------------
        ab    8/10/12   124
        ab    7/10/12   433
        ab    6/10/12    99
        abc   8/10/12    23
        abc   7/10/12    80
  </code></pre>
  
  <p>I would like to query this Model in such a way that i get an output as follows:</p>
  
  <pre><code>[{'item': 'ab', 'values': [ 124, 433, 99]},
   {'item': 'abc', 'values': [ 23, 80]}]
  </code></pre>
  
  <p>How would i be able to do this using the django ORM?</p>