old_contents: import logging; logging.basicConfig(level=logging.INFO)
  
  import asyncio, os, json, time
  
  from datetime import datetime
  
  from aiohttp import web
  
  def index(request):
      return web.Response(body=b'<h1>Welcome!</h1>')
  
  async def init(loop):
      app = web.Application(loop=loop)
      app.router.add_route('GET', '/', index)
      srv = await loop.create_server(app.make_handler(), '', 9000)
      logging.info('Running on http://localhost:9000...')
      return srv
  
  loop = asyncio.get_event_loop()
  loop.run_until_complete(init(loop))
  loop.run_forever()
new_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  
  __author__ = 'Jiayi Li'
  
  import logging; logging.basicConfig(level=logging.INFO)
  
  import asyncio, os, json, time
  
  from datetime import datetime
  
  from aiohttp import web
  
  def index(request):
      return web.Response(body=b'<h1>Welcome!</h1>')
  
  async def init(loop):
      app = web.Application(loop=loop)
      app.router.add_route('GET', '/', index)
      srv = await loop.create_server(app.make_handler(), '', 9000)
      logging.info('Running on http://localhost:9000...')
      return srv
  
  loop = asyncio.get_event_loop()
  loop.run_until_complete(init(loop))
  loop.run_forever()
subject: add header