input: 
  from flask import Flask, jsonify
  import json
  
  def basic_rest_api_countries() -> None:
      """ Create a basic REST API using Python and Flask to list all the countries in the world.
      The API should read the list of countries from a JSON file and return them as a JSON response.
      >>> app = basic_rest_api_countries()
      >>> app.test_client().get('/countries').get_json()
      [{'name': 'Afghanistan', 'code': 'AF'}, {'name': 'Albania', 'code': 'AL'}, ...]
      """
      app = Flask(__name__)
  
      @app.route('/countries', methods=['GET'])
      def get_countries():
          with open('data.json', 'r') as f:
              countries = json.load(f)
          return jsonify(countries)
  
      if __name__ == '__main__':
          app.run()
  
output:     return app