code: def get_connection_string(connection=None):
      
      if not connection:
          config = configparser.ConfigParser()
          cfp = defaults.config_file_path
          if os.path.exists(cfp):
              log.info('fetch database configuration from %s', cfp)
              config.read(cfp)
              connection = config['database']['sqlalchemy_connection_string']
              log.info('load connection string from %s: %s', cfp, connection)
          else:
              with open(cfp, 'w') as config_file:
                  connection = defaults.sqlalchemy_connection_string_default
                  config['database'] = {'sqlalchemy_connection_string': connection}
                  config.write(config_file)
                  log.info('create configuration file %s', cfp)
  
      return connection
docs: return SQLAlchemy connection string if it is set
  
      :param connection: get the SQLAlchemy connection string #TODO
      :rtype: str