* #toMap(Iterable, Function)}.
   *
   * <p>Specifically, for each {@code k} in the backing set, the returned map has an entry mapping
   * {@code k} to {@code function.apply(k)}. The {@code keySet}, {@code values}, and {@code
   * entrySet} views of the returned map iterate in the same order as the backing set.
   *
   * <p>Modifications to the backing set are read through to the returned map. The returned map