code: def published_tracks(self):
          
          if self._published_tracks is None:
              self._published_tracks = PublishedTrackList(
                  self._version,
                  room_sid=self._solution['room_sid'],
                  participant_sid=self._solution['sid'],
              )
          return self._published_tracks
docs: Access the published_tracks
  
          :returns: twilio.rest.video.v1.room.room_participant.room_participant_published_track.PublishedTrackList
          :rtype: twilio.rest.video.v1.room.room_participant.room_participant_published_track.PublishedTrackList