See here for details: https://developers.google.com/webmaster-tools/v3/sitemaps
list_sitemaps(siteURL)
The URL of the website to get sitemap information from. Must include protocol (http://).
A list of two dataframes: $sitemap with general info and $contents with sitemap info.
Other data fetching functions: delete_website
delete_website
Other sitemap admin functions: add_sitemap, delete_sitemap
add_sitemap
delete_sitemap