input: Write a python function to create a Flask API with routes to get and delete items.
  assert app.test_client().get('/items').data == b'["Apple", "Banana", "Orange"]'
  app.test_client().delete('/items/Banana')
  assert app.test_client().get('/items').data == b'["Apple", "Orange"]'
  assert app.test_client().delete('/items/Pineapple').data == b'{"message": "Item not found."}'
  assert app.test_client().delete('/items/Apple').data == b'{"message": "Item successfully deleted."}'
output: from flask import Flask, jsonify, request
  
  app = Flask(__name__)
  
  items = ["Apple", "Banana", "Orange"]
  
  @app.route('/items', methods=['GET'])
  def get_items():
      return jsonify(items)
  
  @app.route('/items/<string:item_name>', methods=['DELETE'])
  def delete_item(item_name):
      if item_name in items:
          items.remove(item_name)
          return jsonify({"message": "Item successfully deleted."})
      else:
          return jsonify({"message": "Item not found."}), 404
  
  if __name__ == '__main__':
      app.run(debug=True)