docs: def use(backend):
      """Use the given database backend, e.g. 'MySQLdb', 'psycopg2',
      'MySQLdb', etc.
      """
      global Backend
  
      try:
          Backend = importlib.import_module(backend)
      except ImportError:
          msg = 'Could not import (load) database.backend: %s' % backend
          raise cfg.AitConfigError(msg)