input: def delete_item_from_list(item: str, items: list) -> dict:
      """
      Delete an item from the list if it exists.
      >>> delete_item_from_list("Banana", ["Apple", "Banana", "Orange"])
      {"message": "Item successfully deleted."}
      >>> delete_item_from_list("Mango", ["Apple", "Banana", "Orange"])
      {"message": "Item not found."}
      """
output:     if item in items:
          items.remove(item)
          return {"message": "Item successfully deleted."}
      else:
          return {"message": "Item not found."}