update ex_2

dart_ex_1/etc.md

@@ -0,0 +1,9 @@
+return SmartLight(id: id, name: name);
+---
+This is poor code naming.
+you should use naming like this. 
+if user provides id and name: user_provided_id, user_provided_name
+So I know the relationship.
+
+
+