docs: def export_obo(path_to_file, connection=None):
      """export database to obo file
  
      :param path_to_file: path to export file
      :param connection: connection string (optional)
      :return:
      """
      db = DbManager(connection)
      db.export_obo(path_to_export_file=path_to_file)
      db.session.close()