title: Django REST, Accessing methods of the selected object
body: <p>this part of my code fills the queryset with [category_object].subcats.all(). let subcats be a method of category object:  </p>
  
  <p>serializer:  </p>
  
  <pre><code>class CatSrlz(serializers.ModelSerializer):
  class Meta:
      model = Category
      fields = ('id', 'label', )  
  </code></pre>
  
  <p>View:  </p>
  
  <pre><code>class CatsViewSet(viewsets.ReadOnlyModelViewSet):
  queryset = Category.objects.filter(parent=None)
  serializer_class = CatSrlz
  
  def retrieve(self, request, *args, **kwargs):
      # return Response({'res': self.kwargs})
      queryset = Category.objects.get(pk=str(self.kwargs['pk'])).subCats.all()
      dt = CatSrlz(queryset, many=True)
      return Response(dt.data)  
  </code></pre>
  
  <p>and url:  </p>
  
  <pre><code>router.register(r'cats', views.CatsViewSet)  
  </code></pre>
  
  <p>it works but i'm pretty sure that there must be a more correct way of doing so
  Is there one?<br>
  thanks</p>