input: 
  def list_all_countries() -> str:
      """ Create a basic REST API using Python and Flask to list all the countries in the world.
      The API should return a JSON response containing all the countries.
      
      Example:
      >>> list_all_countries()
      'import flask\nfrom flask import Flask, request, jsonify\nimport json\n\napp = Flask(__name__)\n\n@app.route('/countries', methods=['GET'])\ndef get_countries():\n with open('data.json', 'r') as f:\n  countries = json.load(f)\n return jsonify(countries)\n\nif __name__ == '__main__':\n app.run()'
      """
  
output:     return '''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()'''