title: proper use of setup_eager_loading
body: <p>I have a serializer which has a nested relationship where 4 additional tables need to be fetched which can create a loop inside loop inside loop and the django ORM is lazy. I thought of using setup_eager_loading to improve the performance. </p>
  
  <p>I have a Eagerloadingmixin as follow </p>
  
  <pre><code>class EagerLoadingMixin:
      @classmethod
      def setup_eager_loading(cls, queryset):
          if hasattr(cls, "SELECT_RELATED"):
              queryset = queryset.select_related(*cls.SELECT_RELATED)
          if hasattr(cls, "PREFETCH_RELATED"):
              queryset = queryset.prefetch_related(*cls.PREFETCH_RELATED)
          return queryset
  
  
  class RentSerializer(serializers.ModelSerializer, EagerLoadingMixin):
      #owner = serializers.SerializerMethodField()
      timeLaps = serializers.SerializerMethodField()
      #gallery = GallerySerializer(read_only=True, many=True)
      #property_category = CategorySerializer()
      SELECT_RELATED = ['owner',]
      PREFETCH_RELATED = ['gallery', 'property_category', ]
      class Meta:
          model = Rental
          read_only = ('id', 'token', 'created_on', 'modified_on', 'slug', )
          fields = ('__all__')
  
  
  class Rent(APIView):
      """
      List all the rents if token is not provided else a token specific rent
      """
      serializer_class = RentSerializer
      def get(self, request, token=None, format=None):
          reply={}
          try:
              rents = Rental.objects.all()
              if token:
                  rent = Rental.objects.get(token=token)
                  reply['data'] = self.serializer_class(rent).data
              else:
                  reply['data'] = self.serializer_class(rents, many=True).data
          except Rental.DoesNotExist:
              return error.RequestedResourceNotFound().as_response()
          except:
              return error.UnknownError().as_response()
          else:
              return Response(reply, status.HTTP_200_OK)
  </code></pre>
  
  <p>How can i use this in my APIView if i am not overriding get_queryset method?</p>