input: Write a python function to create a Flask web application with routes for handling GET and POST requests.
  assert isinstance(app, Flask)
  assert app.url_map.iter_rules().__next__().rule == '/'
  assert app.url_map.iter_rules().__next__().methods == {'GET', 'POST'}
output: def create_flask_app():
      from flask import Flask, request, jsonify
      
      app = Flask(__name__)
  
      @app.route('/', methods=['GET', 'POST'])
      def home():
          if request.method == 'POST':
              data = request.get_json()
              return jsonify(data), 201
          return "Hello, World!", 200
  
      return app
  
  app = create_flask_app()