def save
      data = json_encode(@data)
      FileUtils.mkdir_p File.dirname(@filename)
      PathUtils.atomic_write(@filename) do |f|
        f.write(data)
      end
    end
def save
      data = json_encode(@data)
      FileUtils.mkdir_p File.dirname(@filename)
      PathUtils.atomic_write(@filename) do |f|
        f.write(data)
      end
    end
Persist manfiest back to FS