title: Django, query filtering from model method
body: <p>I have these models:</p>
  
  <pre><code>def Foo(Models.model):
      size = models.IntegerField()
      # other fields
  
      def is_active(self):
           if check_condition:
                return True
           else:
                return False
  
  def Bar(Models.model):
       foo = models.ForeignKey("Foo")
       # other fields
  </code></pre>
  
  <p>Now I want to query Bars that are having active Foo's as such:</p>
  
  <pre><code>Bar.objects.filter(foo.is_active())
  </code></pre>
  
  <p>I am getting error such as</p>
  
  <pre><code>SyntaxError at /
  ('non-keyword arg after keyword arg'
  </code></pre>
  
  <p>How can I achieve this?</p>