Update app.py

app.py

@@ -33,7 +33,7 @@ def my_custom_tool(arg1:str, arg2:int)-> str: #it's import to specify the return
 import requests
 
 @tool
-def get_book() -> List[PotterBook]
+def get_book() -> List[PotterBook]:
     """A tool that fetches the Harry Potter books with information about them.
     Args:
     """