code: def get_flag(var, fallback, expected=True, warn=True):
      
      val = get_config_var(var)
      if val is None:
          if warn:
              warnings.warn("Config variable '{0}' is unset, Python ABI tag may "
                            "be incorrect".format(var), RuntimeWarning, 2)
          return fallback()
      return val == expected
docs: Use a fallback method for determining SOABI flags if the needed config
      var is unset or unavailable.