f wrong check

Author: Boris Pleshakov

rest_framework_json_api/renderers.py

@@ -114,7 +114,7 @@ def extract_relationships(cls, fields, resource, resource_instance):
 
             # Skip fields without relations
             if not isinstance(
-                field, (relations.RelatedField, relations.ManyRelatedField)
+                field, (relations.RelatedField, relations.ManyRelatedField, BaseSerializer)
             ):
                 continue
 
@@ -349,7 +349,7 @@ def extract_included(cls, fields, resource, resource_instance, included_resource
 
             # Skip fields without relations
             if not isinstance(
-                field, (relations.RelatedField, relations.ManyRelatedField)
+                field, (relations.RelatedField, relations.ManyRelatedField, BaseSerializer)
             ):
                 continue