docs: @Nonnull
    private static Configuration _unmarshallConfiguration (@WillClose @Nonnull final InputStream aIS)
    {
      ValueEnforcer.notNull (aIS, "InputStream");
  
      try
      {
        final JAXBContext ctx = JAXBContextCache.getInstance ()
                                                .getFromCache (com.helger.holiday.jaxb.ObjectFactory.class);
        final Unmarshaller um = ctx.createUnmarshaller ();
        final JAXBElement <Configuration> aElement = GenericReflection.uncheckedCast (um.unmarshal (aIS));
        return aElement.getValue ();
      }
      catch (final JAXBException ex)
      {
        throw new IllegalArgumentException ("Cannot parse holidays XML.", ex);
      }
      finally
      {
        StreamHelper.close (aIS);
      }
    }