input: The provided code is a Flask-based REST API for managing a list of items. It includes a route to get the list of items and another route to delete a specified item from the list. Given the context, I will convert this information into a Python function with documentation and example test cases.
  
  
  from flask import Flask, request
  import json
  
  app = Flask(__name__)
  items = ["Apple", "Banana", "Orange"]
  
  @app.route('/items', methods=["GET"])
  def get_items():
      """ Get the list of items. 
      >>> get_items()
      '["Apple", "Banana", "Orange"]'
      """
      return json.dumps(items)
  
  @app.route('/items/<item>', methods=["DELETE"])
  def delete_item(item):
      """ Delete a specified item from the list.
      If the item exists, it deletes the item and returns a success message.
      Otherwise, it returns a message indicating that the item was not found.
      >>> delete_item('Banana')
      '{"message": "Item successfully deleted."}'
      >>> delete_item('Watermelon')
      '{"message": "Item not found."}'
      """
      if item in items:
          items.remove(item)
          message = "Item successfully deleted."
      else:
          message = "Item not found."
      return json.dumps({"message": message})
  
output:     if item in items:
          items.remove(item)
          message = "Item successfully deleted."
      else:
          message = "Item not found."
      return json.dumps({"message": message})