Source

File: wp-includes/sitemaps.php

function wp_sitemaps_get_server() {
	global $wp_sitemaps;

	// If there isn't a global instance, set and bootstrap the sitemaps system.
	if ( empty( $wp_sitemaps ) ) {
		$wp_sitemaps = new WP_Sitemaps();
		$wp_sitemaps->init();

		/**
		 * Fires when initializing the Sitemaps object.
		 *
		 * Additional sitemaps should be registered on this hook.
		 *
		 * @since 5.5.0
		 *
		 * @param WP_Sitemaps $wp_sitemaps Sitemaps object.
		 */
		do_action( 'wp_sitemaps_init', $wp_sitemaps );
	}

	return $wp_sitemaps;
}