public static function setRoot(vfsStreamDirectory $root): vfsStreamDirectory
    {
        self::$root = $root;
        clearstatcache();
        return self::$root;
    }
public static function setRoot(vfsStreamDirectory $root): vfsStreamDirectory
    {
        self::$root = $root;
        clearstatcache();
        return self::$root;
    }
public static function setRoot ( vfsStreamDirectory $ root ) : vfsStreamDirectory { self :: $ root = $ root ; clearstatcache ( ) ; return self :: $ root ; }
sets the root content

@param   vfsStreamDirectory  $root
@return  vfsStreamDirectory
sets the root content