input: from typing import List
  
  def delete_item(items: List[str], item: str) -> str:
      """ Deletes an item from a given list of items and returns a message indicating the result.
      If the item is found in the list, it will be removed and a success message will be returned.
      If the item is not found, a message indicating that the item was not found will be returned.
      >>> delete_item(["Apple", "Banana", "Orange"], "Banana")
      "Item successfully deleted."
      >>> delete_item(["Apple", "Banana", "Orange"], "Grape")
      "Item not found."
      """
output:     if item in items:
          items.remove(item)
          return "Item successfully deleted."
      else:
          return "Item not found."