code: public List<ExtendedRelation> getRelationships() {
  		List<ExtendedRelation> result = null;
  		try {
  			if (extendedRelationsDao.isTableExists()) {
  				result = extendedRelationsDao.queryForAll();
  			} else {
  				result = new ArrayList<>();
  			}
  		} catch (SQLException e) {
  			throw new GeoPackageException("Failed to query for relationships "
  					+ "in " + EXTENSION_NAME, e);
  		}
  		return result;
  	}
docs: Returns the relationships defined through this extension
  
  @return a list of ExtendedRelation objects