title: how do i filter an itertools chain() result?
body: <p>in my views,
  if i import an itertools module:</p>
  
  <pre><code>from itertools import chain
  </code></pre>
  
  <p>and i chain some objects with it:</p>
  
  <pre><code>franktags = Frank.objects.order_by('date_added').reverse().filter(topic__exact='art') 
  amytags = Amy.objects.order_by('date_added').reverse().filter(topic__exact='art') 
  timtags = Tim.objects.order_by('date_added').reverse().filter(topic__exact='art') 
  erictags = Eric.objects.order_by('date_added').reverse().filter(topic__exact='art')
  
  ourtags = list(chain(franktags, amytags, timtags, erictags))
  </code></pre>
  
  <p>how do i then order "ourtags" by the "date_added"?</p>
  
  <p>not surpisingly,</p>
  
  <pre><code>ourtags = list(chain(franktags, amytags, timtags, erictags)).order_by('date_added')
  </code></pre>
  
  <p>returns an "'list' object has no attribute 'order_by'" error.</p>