old_contents: from flask import Flask
  app = Flask(__name__)
  
  @app.route('/')
  def hello_world():
      return 'Hello World'
  
  if __name__ == '__main__':
      app.run(debug=True, host='0.0.0.0')
  
new_contents: from flask import Flask, abort, request
  app = Flask(__name__)
  
  VERIFY_TOKEN = 'temp_token_to_replace_with_secret'
  
  @app.route('/')
  def hello_world():
      return 'Hello World'
  
  @app.route('/webhook/facebook_messenger', methods=['GET', 'POST'])
  def facebook_webhook():
      if request.method == 'POST':
          body = request.get_json()
          if body['object'] == 'page':
              for entry in body['entry']:
                  print(entry['messaging'][0])
              return 'EVENT_RECEIVED'
          abort(404)
      else:
          mode = request.args.get('hub.mode')
          token = request.args.get('hub.verify_token')
          challenge = request.args.get('hub.challenge')
          if mode == 'subscribe' and token == VERIFY_TOKEN:
              return challenge
          abort(403)
  
  if __name__ == '__main__':
      app.run(debug=True, host='0.0.0.0')
  
subject: Set up basic webhook for Messenger