title: Django-filter error: 'Meta.fields' must not contain non-model field names
body: <p>I am working with Django REST framework and django-filters and and I'd like to use the reverse relationship <code>annotation_set</code> as one of filters for a <code>GET</code> API that uses the model <code>Detection</code>.
  The models are the following:</p>
  <pre><code>class Detection(models.Model):
      image = models.ImageField(upload_to=&quot;detections/images&quot;)
  
      def local_image_path(self):
          return os.path.join('images' f&quot;{self.id}.jpg&quot;)
  
  
  class Annotation(models.Model):
      detection = models.ForeignKey(Detection, on_delete=models.CASCADE)
      attribute = models.CharField(max_length=255)
  </code></pre>
  <p>The serializer is:</p>
  <pre><code>class DetectionSerializer(UniqueFieldsMixin, serializers.ModelSerializer):
      local_image_path = serializers.CharField()
  
      class Meta:
          model = Detection
          fields = '__all__'
  
  </code></pre>
  <p>And the viewset is:</p>
  <pre><code>
  class DetectionTrainingViewSet(
          mixins.ListModelMixin,
          mixins.RetrieveModelMixin,
          viewsets.GenericViewSet
      ):
      queryset = Detection.objects.all()
      serializer_class = DetectionSerializer
      filterset_fields = ('annotation_set__id', )
  
      @action(methods=['GET'], detail=False)
      def list_ids(self, request):
          queryset = self.get_queryset()
          filtered_queryset = self.filter_queryset(queryset)
          return Response(filtered_queryset.values_list('id', flat=True))
  </code></pre>
  <p>When I make a call to the endpoint, I get the error:</p>
  <pre><code>'Meta.fields' must not contain non-model field names: annotation_set__id
  </code></pre>
  <p>Shouldn't the field exist?
  Note: I tried to add other fields to the <code>Annotation</code> model and then use <code>annotation_set__newfield</code> but I still have the error. I can confirm that the <code>newfield</code> exists because it is correctly serialized and return by the API when I comment out the line that set the <code>filterset_fields</code>.</p>