code: public List<ContentsId> getIds() {
  		List<ContentsId> contentsIds = null;
  		try {
  			if (contentsIdDao.isTableExists()) {
  				contentsIds = contentsIdDao.queryForAll();
  			} else {
  				contentsIds = new ArrayList<>();
  			}
  		} catch (SQLException e) {
  			throw new GeoPackageException(
  					"Failed to query for all contents ids. GeoPackage: "
  							+ geoPackage.getName(), e);
  		}
  		return contentsIds;
  	}
docs: Get all contents ids
  
  @return contents ids