code: private void addNonPermanent(AddOnModel addOnModel, IzouSoundLineBaseClass izouSoundLine) {
          debug("adding " + izouSoundLine + " from " + addOnModel + " to non-permanent");
          if (izouSoundLine.isPermanent())
              izouSoundLine.setToNonPermanent();
          List<WeakReference<IzouSoundLineBaseClass>> weakReferences = nonPermanent.get(addOnModel);
          if (weakReferences == null)
              weakReferences = Collections.synchronizedList(new ArrayList<>());
          nonPermanent.put(addOnModel, weakReferences);
          weakReferences.add(new WeakReference<>(izouSoundLine));
      }
docs: adds the IzouSoundLine as NonPermanent
  @param addOnModel the AddonModel to
  @param izouSoundLine the IzouSoundLine to add