private void Player_MarkerLeft(object player, CustomEventArgs <TimelineMediaMarker> args)
 {
     MarkerLeft.IfNotNull(i =>
     {
         var mm = new ScriptMediaMarker(args.Value);
         i(this, new ScriptEventArgs <ScriptMediaMarker>(mm));
     });
 }
 protected virtual void OnMarkerLeft(TMediaMarker mediaMarker)
 {
     MarkerLeft.IfNotNull(i => i(this, mediaMarker));
 }