title: Django Rest how to order on a model method
body: <p>Using Django Rest Framework is it possible to <code>order</code> on a model method? I have tried it and DRF requires it to be field. So gives the error:</p>
  
  <blockquote>
    <p>Cannot resolve keyword 'distance' into field.</p>
  </blockquote>
  
  <p><strong>View</strong> 
      class ActivityListView(ListCreateView):</p>
  
  <pre><code>    queryset = model_activity.objects.all()
      serializer_class = ActivityListSerializer
      filter_backends = (OrderingFilter,)
      # default ordering
      ordering = ('distance')
  </code></pre>
  
  <p><strong>Serializer</strong></p>
  
  <pre><code>class ActivityListSerializer(serializers.ModelSerializer):
  
      distance = serializers.SerializerMethodField('_get_distance')
  
      class Meta:
          model = model_activity
          fields = ('id', 'distance')
  
      def _get_distance(self, obj):
          return obj.get_distance(user=self.context['request'].user)
  </code></pre>