code: private List<AbstractItem> getRawItems() {
          if (rawItems == null) {
              rawItems = new ArrayList<>();
  
              for (int i = 0; i < items.size(); i++) {
                  AbstractItem item = items.get(i);
  
                  if (item instanceof Divider && columnCount > 1) {
                      for (int j = 0; j < rawItems.size() % columnCount; j++) {
                          rawItems.add(null);
                      }
  
                      rawItems.add(item);
  
                      for (int j = 0; j < columnCount - 1; j++) {
                          rawItems.add(new Divider());
                      }
                  } else {
                      rawItems.add(item);
                  }
              }
          }
  
          return rawItems;
      }
docs: Returns a list, which contains the items of the adapter including placeholders.
  
  @return A list, which contains the items of the adapter including placeholders, as an
  instance of the type {@link List} or an empty list, if the adapter contains no items