input: from flask import Flask, request
  import json
  
  app = Flask(__name__)
  items = ["Apple", "Banana", "Orange"]
  
  @app.route('/items/<item>', methods=["DELETE"])
  def delete_item(item):
      """This function deletes an item from the 'items' list if it exists and returns a message indicating 
      whether the item was successfully deleted or if it was not found.
      >>> delete_item('Banana')
      '{"message": "Item successfully deleted."}'
      >>> delete_item('Grape')
      '{"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})