* iterable is empty, {@code Optional.absent()} is returned. If the underlying {@code iterable} is
   * a {@link List} with {@link java.util.RandomAccess} support, then this operation is guaranteed
   * to be {@code O(1)}.
   *
   * <p><b>{@code Stream} equivalent:</b> {@code stream.reduce((a, b) -> b)}.
   *

   * toString} methods for the multimap and its returned views. The multimap's {@code get}, {@code
   * removeAll}, and {@code replaceValues} methods return {@code RandomAccess} lists if the factory
   * does. However, the multimap's {@code get} method returns instances of a different class than
   * does {@code factory.get()}.
   *