old_contents: from flask import Flask, render_template
  
  app = Flask(__name__)
  app.template_folder = '../frontend'
  
  
  @app.route("/")
  def hello():
      return render_template('index.html')
  
  if __name__ == "__main__":
      app.run(host='0.0.0.0', port=5000, debug=True)
  
new_contents: from flask import Flask, render_template
  
  app = Flask(__name__)
  app.template_folder = '../frontend'
  
  @app.route("/")
  def hello():
      return render_template('index.html')
  
  if __name__ == "__main__":
      app.run(host='0.0.0.0', port=5000, debug=True)
  
subject: Update app.py