docs: def dsn():
      """
      Return a libpq connection string using the variables defined in this file.
      """
      configs = {'host': host,
                 'port': port,
                 'dbname': database,
                 'user': user,
                 'password': password}
      return ' '.join(['{0}={1}'.format(_[0], _[1]) for _ in configs.items() if _[1] is not None and _[1] != ''])