code: def argument_parser():
      
      parser = argparse.ArgumentParser(
          description='openssl wrapper')
      parser.add_argument('--ca', action='store_true', default=False,
                          dest='is_ca',
                          help='Is it a Certificate Authority certificate?')
      parser.add_argument('-f', '--filename', type=str, default='localhost',
                          help='File name prefix of the key and certificate.')
      parser.add_argument('-d', '--dirname', type=str, default=DEFAULT_CERTS_DIR,
                          help='Destination directory name.')
      parser.add_argument('--days', type=int, default=500,
                          help='Duration of certificate.')
      parser.add_argument('--ip', nargs='*', default=['127.0.0.1'],
                          help='IP address.')
      parser.add_argument('--dns', nargs='*', default=['localhost'],
                          help='DNS')
      parser.add_argument('--silent', action='store_true',
                          help='should the output from the shell be silenced?')
      return parser
docs: process the command line arguments.
      :returns: an ArgumentParser object.