code: public static void forEachURLSet (@Nonnull final Consumer <? super XMLSitemapURLSet> aConsumer)
    {
      ValueEnforcer.notNull (aConsumer, "Consumer");
      for (final IXMLSitemapProviderSPI aSPI : s_aProviders)
      {
        final XMLSitemapURLSet aURLSet = aSPI.createURLSet ();
        aConsumer.accept (aURLSet);
      }
    }
docs: Create URL sets from every provider and invoke the provided consumer with
  it.
  
  @param aConsumer
  The consumer to be invoked. Must be able to handle <code>null</code>
  and empty values. May itself not be <code>null</code>.