code: protected Extensions get(String extensionName, String tableName,
  			String columnName) {
  
  		Extensions extension = null;
  		try {
  			if (extensionsDao.isTableExists()) {
  				extension = extensionsDao.queryByExtension(extensionName,
  						tableName, columnName);
  			}
  		} catch (SQLException e) {
  			throw new GeoPackageException("Failed to query for '"
  					+ extensionName + "' extension for GeoPackage: "
  					+ geoPackage.getName() + ", Table Name: " + tableName
  					+ ", Column Name: " + columnName, e);
  		}
  		return extension;
  	}
docs: Get the extension for the name, table name, and column name
  
  @param extensionName
  extension name
  @param tableName
  table name
  @param columnName
  column name
  @return extension