When usingPolymorphicModelSerializer withJSONRenderer, theextract_included method is retrieving the base polymorphic serializer instead of the specific serializer corresponding to the object instance. This results in theincludes not being processed correctly, as the base polymorphic serializer is not equipped to handle the specifics of each derived instance.

It appears that the issue can be resolved by modifying therender method to correctly identify and use the appropriate serializer based on the object instance during the rendering process. This adjustment should enableincludes to function as expected with polymorphic serializers.

if serializer is not None:    # Extract root meta for any type of serializer    json_api_meta.update(self.extract_root_meta(serializer, serializer_data))    if getattr(serializer, "many", False):        ...    else:        if isinstance(serializer, PolymorphicModelSerializer):            resource_instance = serializer.instance            serializer_class = serializer.get_polymorphic_serializer_for_instance(resource_instance)            serializer = serializer_class(resource_instance, context=serializer.context)            fields = utils.get_serializer_fields(serializer)            ...