code: @Override
      public NamespaceGroup convert(XBELNamespaceGroup source) {
          if (source == null) return null;
  
          String defaultResourceLocation = source.getDefaultResourceLocation();
          List<XBELNamespace> xbelnamespaces = source.getNamespace();
  
          NamespaceGroup dest = new NamespaceGroup();
          int size = xbelnamespaces.size();
          final List<Namespace> namespaces = new ArrayList<Namespace>(size);
  
          NamespaceConverter nsConverter = new NamespaceConverter();
          for (final XBELNamespace xns : xbelnamespaces) {
              // Defer to NamespaceConverter
              namespaces.add(nsConverter.convert(xns));
          }
  
          dest.setDefaultResourceLocation(defaultResourceLocation);
          dest.setNamespaces(namespaces);
          return dest;
      }
docs: {@inheritDoc}