title: Django model multiply filter
body: <p>I want to filter my model object using two filters.
  So, it can be only one filter or both or none.
  My solution is to use a lot of 'if':</p>
  
  <pre><code>if _topic or _curator:
      if _topic and _curator:
          queryset = Article.objects.filter(topic=_topic,curator=_curator)
      elif _curator:
          queryset = Article.objects.filter(curator=_curator)
      else # so topic is the last choice
          queryset = Article.objects.filter(topic=_topic)
  else
      queryset = Article.objects.all()
  </code></pre>
  
  <p>Can someone suggest an easier way to filter?</p>