static <T> Writer<Iterable<T>> elems(final Writer<? super T> writer) {
		requireNonNull(writer);

		return (xml, data) -> {
			if (data != null) {
				for (T value : data) {
					if (value != null) {
						writer.write(xml, value);
					}
				}
			}
		};
	}
Creates a new {@code Writer}, which writes the given {@code children} as
sub-elements, defined by the given {@code childWriter}.

@param writer the sub-element writer
@param <T> the writer base type
@return a new writer instance
@throws NullPointerException if one of the arguments is {@code null}
jenetics.xml/src/main/java/io/jenetics/xml/stream/Writer.java