code: public TileSet getTileSet (int tileSetId)
          throws NoSuchTileSetException
      {
          // make sure we have a repository configured
          if (_setrep == null) {
              throw new NoSuchTileSetException(tileSetId);
          }
  
          try {
              return _setrep.getTileSet(tileSetId);
          } catch (PersistenceException pe) {
              log.warning("Failure loading tileset", "id", tileSetId, "error", pe);
              throw new NoSuchTileSetException(tileSetId);
          }
      }
docs: Returns the tileset with the specified id. Tilesets are fetched from the tileset repository
  supplied via {@link #setTileSetRepository}, and are subsequently cached.
  
  @param tileSetId the unique identifier for the desired tileset.
  
  @exception NoSuchTileSetException thrown if no tileset exists with the specified id or if
  an underlying error occurs with the tileset repository's persistence mechanism.