code: public TileMatrixSet getTileMatrixSet() {
  		TileMatrixSet result = null;
  		if (tileMatrixSet.size() > 1) {
  			// This shouldn't happen with the table name primary key on tile
  			// matrix set
  			throw new GeoPackageException(
  					"Unexpected state. More than one TileMatrixSet has a foreign key to the Contents. Count: "
  							+ tileMatrixSet.size());
  		} else if (tileMatrixSet.size() == 1) {
  			CloseableIterator<TileMatrixSet> iterator = tileMatrixSet
  					.closeableIterator();
  			try {
  				result = iterator.next();
  			} finally {
  				try {
  					iterator.close();
  				} catch (IOException e) {
  					throw new GeoPackageException(
  							"Failed to close the Tile Matrix Set iterator", e);
  				}
  			}
  		}
  		return result;
  	}
docs: Get the Tile Matrix Set, should only return one or no value
  
  @return tile matrix set