code: public <T> FluentIterable<T> transformAndConcat(
        Function<? super E, ? extends Iterable<? extends T>> function) {
      return from(FluentIterable.concat(transform(function)));
    }
docs: Applies {@code function} to each element of this fluent iterable and returns a fluent iterable
  with the concatenated combination of results. {@code function} returns an Iterable of results.
  
  <p>The returned fluent iterable's iterator supports {@code remove()} if this function-returned
  iterables' iterator does. After a successful {@code remove()} call, the returned fluent
  iterable no longer contains the corresponding element.
  
  <p><b>{@code Stream} equivalent:</b> {@link Stream#flatMap} (using a function that produces
  streams, not iterables).
  
  @since 13.0 (required {@code Function<E, Iterable<T>>} until 14.0)