}

    private FileSystemLocationSnapshot snapshot(String location, SnapshottingFilter filter) {
        ImmutableMap<String, FileSystemLocationSnapshot> previouslyKnownSnapshots = virtualFileSystem
            .findRootSnapshotsUnder(location)
            .collect(ImmutableMap.toImmutableMap(
                FileSystemLocationSnapshot::getAbsolutePath,
                Function.identity()
            ));