Add type annotation

app.py

@@ -63,8 +63,8 @@ default_style = styles[default_style_name]
 style_names = list(styles.keys())
 
 
-def apply_style(style, positive, negative=""):
-    p, n = styles.get(style, default_style)
+def apply_style(style_name: str, positive: str, negative: str = "") -> tuple[str, str]:
+    p, n = styles.get(style_name, default_style)
     return p.replace("{prompt}", positive), n + negative