docs: private void generatePrices(final Metadata m, final Element e) {
          for (final Price price : m.getPrices()) {
              if (price == null) {
                  continue;
              }
              final Element priceElement = new Element("price", NS);
              if (price.getType() != null) {
                  priceElement.setAttribute("type", price.getType().name().toLowerCase());
              }
              addNotNullAttribute(priceElement, "info", price.getInfo());
              addNotNullAttribute(priceElement, "price", price.getPrice());
              addNotNullAttribute(priceElement, "currency", price.getCurrency());
              if (priceElement.hasAttributes()) {
                  e.addContent(priceElement);
              }
          }
      }