diff --git a/naive-nlu/tree_nlu/utils/json_dumper.py b/naive-nlu/tree_nlu/utils/json_dumper.py
new file mode 100644
index 0000000..061dd68
--- /dev/null
+++ b/naive-nlu/tree_nlu/utils/json_dumper.py
@@ -0,0 +1,4 @@
+def dumper(obj):
+    if isinstance(obj, set):
+        return list(obj)
+    return obj