input: def list_countries_api():
      """
      Create a basic REST API using Python and Flask to list all the countries in the world.
      >>> list_countries_api()
      """
      import flask
      from flask import Flask, request, jsonify
      import json
  
      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
  