code: def post(self):
      username = self.get_argument("username", "")
      password = self.get_argument("password", "")
      auth = self.check_permission(username, password)
      if auth:
          self.set_current_user(username)
          self.redirect("/")
      else:
          error_msg = "?error=" + tornado.escape.url_escape(
              "Login incorrect"
          )
          self.redirect(login_url + error_msg)
  
file_path: bokeh/examples/server/app/server_auth/auth.py
imports: import tornado
  from tornado.web import RequestHandler
label_desc: Use image node_id 3 for calling the LoginHandler obj's underlying member method code with example usage: obj.post() without return types