input: Write a function to create a REST API in Python that can be used to delete an item from a list. The function should define the GET and DELETE routes, where the GET route returns the list of items and the DELETE route removes a specified item from the list. If the item is not found, the DELETE route should return a message indicating the item was not found.
  assert app.get_items() == '["Apple", "Banana", "Orange"]'
  assert app.delete_item("Apple") == '{"message": "Item successfully deleted."}'
  assert app.delete_item("Grape") == '{"message": "Item not found."}'
  assert app.get_items() == '["Banana", "Orange"]'
output: def get_items():
      return '["Apple", "Banana", "Orange"]'
  
  def delete_item(item):
      items = ["Apple", "Banana", "Orange"]
      if item in items:
          items.remove(item)
          return '{"message": "Item successfully deleted."}'
      else:
          return '{"message": "Item not found."}'