Update app.py

_js=js -> js=js

app.py

@@ -22,7 +22,7 @@ with gr.Blocks(theme='ParityError/Anime') as demo:
                 dropdown.render()
                 toggle_dark = gr.Button(value="Toggle Dark", scale=1)
 
-    dropdown.change(None, dropdown, None, _js=js)
+    dropdown.change(None, dropdown, None, js=js)
     toggle_dark.click(
         None,
         _js="""