各位大仙们，看看下面的这段代码是否是 tornado 异步的代码？

#!/usr/bin/env python3

import os
import urllib.parse

import tornado.gen
import tornado.escape
import tornado.httpclient
import tornado.ioloop
import tornado.web
from base import BaseHandler

from config import web as config
import db
import rs
import qntoken
from auth import auth_required

from lib.utils import Validators
import random
from lib.desdec import *

class MainHandler(BaseHandler):
    #@auth_required
    @tornado.gen.coroutine
    def get(self):
        user_rows = yield self.db.get_userlist()
        self.set_header('Content-Type', 'application/json')
        self.write(tornado.escape.json_encode(user_rows))