 of ``path`` relative to ``root``.

        ``root`` is the path configured for this `StaticFileHandler`
        (in most cases the ``static_path`` `Application` setting).

        This class method may be overridden in subclasses.  By default
        it returns a filesystem path, but other strings may be used
        as long as they are unique and understood by the subclass's
        overridden `get_content`.

        .. versionadded:: 3.1
        N)