old_contents: import webapp2
  
  class MainPage(webapp2.RequestHandler):
      def get(self):
          self.response.headers['Content-Type'] = 'text/plain'
          self.response.write('Hello, World!')
  
  app = webapp2.WSGIApplication([
      ('/', MainPage),
  ], debug=True)
  
new_contents: import webapp2
  
  class MainPage(webapp2.RequestHandler):
      def get(self):
          self.response.headers['Content-Type'] = 'text/plain'
          self.response.write('Hello, World!\nWelcome to Mech AI.')
  
  app = webapp2.WSGIApplication([
      ('/', MainPage),
  ], debug=True)
  
subject: Test update source