Flat Mapping

Our topology is almost complete! For the next part, we’ll transform single records from each of the two streams we have into a list of feelings associated with them:

• For the instrumental tracks, we’ll use Api::getFeelingsById, which returns List<Feeling>.

• For the noninstrumental tracks, which we mapped to lyrics in the previous lesson, we’ll use Api::getFeelingsByLyrics, which also returns List<Feeling>.