diff --git a/DesignPattern/Decorator/duck_typing.py b/DesignPattern/Decorator/duck_typing.py
index 857720b..eca56de 100644
--- a/DesignPattern/Decorator/duck_typing.py
+++ b/DesignPattern/Decorator/duck_typing.py
@@ -15,3 +15,13 @@
 
 
 # 内部ライブラリ
+
+class Specialstring:
+    def __len__(self):
+        return 21
+
+
+# Driver's code
+if __name__ == "__main__":
+    string = Specialstring()
+    print(len(string))
diff --git a/DesignPattern/Decorator/formatting_tool.py b/DesignPattern/Decorator/formatting_tool.py
index a349d63..c1065bc 100644
--- a/DesignPattern/Decorator/formatting_tool.py
+++ b/DesignPattern/Decorator/formatting_tool.py
@@ -61,6 +61,7 @@ def render(self):
 
 if __name__ == '__main__':
     before_gfg = WrittenText("GeeksforGeeks")
+
     after_gfg = ItalicWrapper(UnderlineWrapper(BoldWrapper(before_gfg)))
 
     print("before :", before_gfg.render())