private static MultimapBuilderWithKeys<Comparable<?>> rawtypeToWildcard(
      MultimapBuilderWithKeys<Comparable> treeKeys) {
    return (MultimapBuilderWithKeys) treeKeys;
  }

  @SuppressWarnings({"rawtypes", "unchecked"})
  private static <K extends @Nullable Object>
      SortedSetMultimapBuilder<K, Comparable<?>> rawtypeToWildcard(
          SortedSetMultimapBuilder<K, Comparable> setMultimapBuilder) {