input: 
  import flask
  from flask import Flask, request, jsonify
  import json
  
  app = Flask(__name__)
  
  @app.route('/countries', methods=['GET'])
  def get_countries():
      """This function creates a basic REST API using Python and Flask to list all the countries in the world.
      The countries are stored in a JSON file named 'data.json'.
      
      Example:
      If 'data.json' contains:
      [
          {"name": "United States"},
          {"name": "Canada"},
          {"name": "Mexico"}
      ]
      Then, a GET request to '/countries' will return:
      {
          "countries": [
              {"name": "United States"},
              {"name": "Canada"},
              {"name": "Mexico"}
          ]
      }
      """
      with open('data.json', 'r') as f:
          countries = json.load(f)
      return jsonify(countries)
  
  if __name__ == '__main__':
      app.run()
  
output:     
      with open('data.json', 'r') as f:
          countries = json.load(f)
      return jsonify(countries)
  