def add_extra_urls(self, item_session: ItemSession):
        '''Add additional URLs such as robots.txt, favicon.ico.'''

        if item_session.url_record.level == 0 and self._sitemaps:
            extra_url_infos = (
                self.parse_url(
                    '{0}://{1}/robots.txt'.format(
                        item_session.url_record.url_info.scheme,
                        item_session.url_record.url_info.hostname_with_port)
                ),
                self.parse_url(
                    '{0}://{1}/sitemap.xml'.format(
                        item_session.url_record.url_info.scheme,
                        item_session.url_record.url_info.hostname_with_port)
                )
            )

            for url_info in extra_url_infos:
                item_session.add_child_url(url_info.url)
Add additional URLs such as robots.txt, favicon.ico.