code: private static TileGroup importGroup(Xml nodeGroup)
      {
          final Collection<Xml> children = nodeGroup.getChildren(TileConfig.NODE_TILE);
          final Collection<TileRef> tiles = new ArrayList<>(children.size());
  
          for (final Xml nodeTileRef : children)
          {
              final TileRef tileRef = TileConfig.imports(nodeTileRef);
              tiles.add(tileRef);
          }
  
          final String groupName = nodeGroup.readString(ATT_GROUP_NAME);
          final TileGroupType groupType = TileGroupType.from(nodeGroup.readString(TileGroupType.NONE.name(),
                                                                                  ATT_GROUP_TYPE));
          return new TileGroup(groupName, groupType, tiles);
      }
docs: Import the group from its node.
  
  @param nodeGroup The group node (must not be <code>null</code>).
  @return The imported group.