code: def get_flag(var, fallback, expected=True, warn=True):
      
      val = get_config_var(var)
      if val is None:
          if warn:
              log.debug("Config variable '%s' is unset, Python ABI tag may "
                        "be incorrect", var)
          return fallback()
      return val == expected
docs: Use a fallback method for determining SOABI flags if the needed config
      var is unset or unavailable.