return ImmutableList.of(value, value);
    }
  }

  public void testTransformAndConcat() {
    List<Integer> input = asList(1, 2, 3);
    Iterable<String> result =
        FluentIterable.from(input).transformAndConcat(new RepeatedStringValueOfFunction());
    assertEquals(asList("1", "1", "2", "2", "3", "3"), Lists.newArrayList(result));
  }

  private static final class RepeatedStringValueOfWildcardFunction

   * streams, not iterables).
   *
   * @since 13.0 (required {@code Function<E, Iterable<T>>} until 14.0)
   */
  public <T extends @Nullable Object> FluentIterable<T> transformAndConcat(
      Function<? super E, ? extends Iterable<? extends T>> function) {
    return FluentIterable.concat(transform(function));
  }

  /**