old_contents: from calm_temple_8514 import app
  from flask import render_template, request, make_response,redirect, url_for
  from time import time
  
  #Index
  @app.route('/')
  def index(username=None):
      resp = make_response(render_template('index.html'))
      resp.set_cookie('visit', str(time()))
      return resp
  
  @app.route('/username', methods=['POST'])
  def username():
      return NotImplementedError
  
  #404
  @app.errorhandler(404)
  def page_not_found(error):
      return render_template('404.html'), 404
  
new_contents: from calm_temple_8514 import app
  from flask import render_template, request, make_response,redirect, url_for
  from time import time
  
  #Index
  @app.route('/')
  def index(username=None):
      resp = make_response(render_template('index.html'))
      resp.set_cookie('visit', str(time()))
      return resp
      
  #Redirect to the FluidUI mock
  @app.route('/mock')
  def mock():
      url = "https://www.fluidui.com/editor/live/preview/p_8dsgi7txTgebKJbBuOOBb2a2rsLTvEFz.1455096789274"
      return redirect(url, code=302)
  
  @app.route('/username', methods=['POST'])
  def username():
      return NotImplementedError
  
  #404
  @app.errorhandler(404)
  def page_not_found(error):
      return render_template('404.html'), 404
  
subject: Update index.py