code: def pg_dsn(settings: Settings) -> str:
      
      return str(URL(
          database=settings.DB_NAME,
          password=settings.DB_PASSWORD,
          host=settings.DB_HOST,
          port=settings.DB_PORT,
          username=settings.DB_USER,
          drivername='postgres',
      ))
docs: :param settings: settings including connection settings
      :return: DSN url suitable for sqlalchemy and aiopg.