How to tell MediaItem.SubtitleConfigurations apart in ExoPlayer.getCurrentTracksInfo().getTrackGroupInfos()? #9673

I'm using latest ExoPlayer 2.16.0. Let's say I want to save and restore user selected audio and subtitle "tracks" on app restart. If I add multiple MediaItem.SubtitleConfigurations, how I can I distinguish these in ExoPlayer.getCurrentTracksInfo().getTrackGroupInfos()?

Format(null, null, null, application/x-subrip, null, -1, null, [-1, -1, -1.0], [-1, -1])
Format(null, null, null, application/x-subrip, null, -1, null, [-1, -1, -1.0], [-1, -1])

MediaItem.SubtitleConfiguration doesn't let me specify any id. Label or user facing name may not be necessarily unique, especially if I allow users loading subtitles. The only difference may be the subtitle content/uri.

In ExoPlayer 2.15.1, I was able to tell a difference from DefaultTrackSelector.SelectionOverride.groupIndex.