docs: void addLastEntry(Object entry) {
          if (multiple == null) {
              if (!single.equals(entry)) {
                  multiple = new LinkedList<Object>();
                  multiple.addLast(single);
                  multiple.addLast(entry);
              }
          } else {
              if (!multiple.contains(entry)) {
                  multiple.addLast(entry);
              }
          }
          single = entry;
      }