# isInvalidTokenError method Null safety

bool isInvalidTokenError()

## Implementation

    bool isInvalidTokenError() {
      if (this is KakaoAuthException &&
          (this as KakaoAuthException).error == AuthErrorCause.invalidGrant) {
        return true;
      } else if (this is KakaoApiException &&
          (this as KakaoApiException).code == ApiErrorCause.invalidToken) {
        return true;
      }
      return false;
    }