input: 
  def delete_item_from_list(item_name: str, items: List[str]) -> str:
      """ Deletes a specified item from the given list of items.
      If the item is found and deleted, it returns a message indicating successful deletion.
      Otherwise, it returns a message indicating that the item was not found.
      >>> delete_item_from_list("Apple", ["Apple", "Banana", "Orange"])
      "Item successfully deleted."
      >>> delete_item_from_list("Mango", ["Apple", "Banana", "Orange"])
      "Item not found."
      """
  
output:     if item_name in items:
          items.remove(item_name)
          return "Item successfully deleted."
      else:
          return "Item not found."