Filter to append sitemaps to the index. Parameters $index ( string ) String to append to sitemaps index, defaults to empty. . . . Hook name: wpseo_sitemap_index Hook type: filter Plugin ref: Yoast SEO Sourcefile: File ref: WPSEO_Sitemaps_Renderer::get_index() – Builds the sitemap index. Description: Filter to append sitemaps to the index. Parameters: Deprecated?: No API Letters: I,S,W Invokers 1 to 1 of 1 WPSEO_Sitemaps_Renderer::get_index() – Builds the sitemap index. Implementers