get_block_theme_folders() WordPress Function

function get_block_theme_folders( $theme_stylesheet = null ) {
	$theme_name = null === $theme_stylesheet ? get_stylesheet() : $theme_stylesheet;
	$root_dir   = get_theme_root( $theme_name );
	$theme_dir  = "$root_dir/$theme_name";

	if ( file_exists( $theme_dir . '/block-templates' ) || file_exists( $theme_dir . '/block-template-parts' ) ) {
		return array(
			'wp_template'      => 'block-templates',
			'wp_template_part' => 'block-template-parts',
		);
	}

	return array(
		'wp_template'      => 'templates',
		'wp_template_part' => 'parts',
	);
}