docs: def get_pytwis(epilog):
      """Connect to the Redis database and return the Pytwis instance.
  
      Parameters
      ----------
      epilog: str
          An epilog string which will be displayed by ArgumentParser.
  
      Returns
      -------
      pytwis: A Pytwis instance.
      prompt: str
          The prompt string which contains either the hostname and the port or the socket.
      Raises
      ------
      ValueError
          If we fail to connect to the Redis server.
      """
      # Note that we set the conflict handler of ArgumentParser to 'resolve' because we reuse
      # the short help option '-h' for the host name.
      parser = argparse.ArgumentParser(conflict_handler="resolve",
                                       formatter_class=argparse.RawDescriptionHelpFormatter,
                                       description=\
                                       'Connect to the Redis database of a Twitter clone and '
                                       'then run commands to access and update the database.',
                                       epilog=epilog)
      parser.add_argument('-h', '--hostname', nargs='?', default='127.0.0.1',
                          help='''the Redis server hostname. If the option is not specified,
                               will be defaulted to 127.0.0.1. If the option is specified but
                               no value is given after the option, then the help information
                               is displayed instead.
                               ''')
      parser.add_argument('-p', '--port', default=6379,
                          help='''the Redis server port. If the option is not specified, will
                               be defaulted to 6379.
                               ''')
      parser.add_argument('-s', '--socket', default='',
                          help='''the Redis server socket (usually /tmp/redis.sock). If it is
                               given, it will override hostname and port. Make sure that the
                               unixsocket parameter is defined in your redis.conf file. It’s
                               commented out by default.
                               ''')
      parser.add_argument('-n', '--db', default=0,
                          help='''the Redis server database. If the option is not specified,
                               will be defaulted to 0.
                               ''')
      parser.add_argument('-a', '--password', default='',
                          help='''the Redis server password. If the option not specified,
                               will be defaulted to an empty string.
                               ''')
  
      args = parser.parse_args()
  
      # If no value is given after the option '-h', then the help information is displayed.
      if args.hostname is None:
          parser.print_help()
          return 0
  
      if args.socket:
          print('The input Redis server socket is {}'.format(args.socket))
          prompt = args.socket
      else:
          print('The input Redis server hostname is {}.'.format(args.hostname))
          print('The input Redis server port is {}.'.format(args.port))
          prompt = '{}:{}'.format(args.hostname, args.port)
      print('The input Redis server database is {}.'.format(args.db))
      if args.password != '':
          print('The input Redis server password is "{}".'.format(args.password))
      else:
          print('The input Redis server password is empty.')
  
      try:
          if args.socket:
              twis = pytwis.Pytwis(socket=args.socket,
                                   db=args.db,
                                   password=args.password)
          else:
              twis = pytwis.Pytwis(hostname=args.hostname,
                                   port=args.port,
                                   db=args.db,
                                   password=args.password)
          return twis, prompt
  
      except ValueError as excep:
          print('Failed to connect to the Redis server: {}'.format(str(excep)),
                file=sys.stderr)
          return None, None