code: def serialize_options(opts):
      
      options = (opts or {}).copy()
  
      for key in opts.keys():
          if key not in DEFAULT_OPTIONS:
               LOG.warning("Unknown option passed to Flask-CORS: %s", key)
  
      # Ensure origins is a list of allowed origins with at least one entry.
      options['origins'] = sanitize_regex_param(options.get('origins'))
      options['allow_headers'] = sanitize_regex_param(options.get('allow_headers'))
  
      # This is expressly forbidden by the spec. Raise a value error so people
      # don't get burned in production.
      if r'.*' in options['origins'] and options['supports_credentials'] and options['send_wildcard']:
          raise ValueError("Cannot use supports_credentials in conjunction with"
                           "an origin string of '*'. See: "
                           "http://www.w3.org/TR/cors/#resource-requests")
  
  
  
      serialize_option(options, 'expose_headers')
      serialize_option(options, 'methods', upper=True)
  
      if isinstance(options.get('max_age'), timedelta):
          options['max_age'] = str(int(options['max_age'].total_seconds()))
  
      return options
docs: A helper method to serialize and processes the options dictionary.