code: private static Collection<TileRef> importTiles(Collection<Xml> nodesTileRef)
      {
          final Collection<TileRef> tilesRef = new HashSet<>(nodesTileRef.size());
  
          for (final Xml nodeTileRef : nodesTileRef)
          {
              final TileRef tileRef = TileConfig.imports(nodeTileRef);
              tilesRef.add(tileRef);
          }
  
          return tilesRef;
      }
docs: Import all tiles from their nodes.
  
  @param nodesTileRef The tiles nodes (must not be <code>null</code>).
  @return The imported tiles ref.