private static boolean isUnknownStatusCode(final int status) {
        if (status >= 100 && status <= 101) {
            return false;
        }
        if (status >= 200 && status <= 206) {
            return false;
        }
        if (status >= 300 && status <= 307) {
            return false;
        }
        if (status >= 400 && status <= 417) {
            return false;
        }
        return status < 500 || status > 505;
    }
Determine if the {@link HttpResponse} gotten from the origin is a
cacheable response.

@return {@code true} if response is cacheable
httpclient5-cache/src/main/java/org/apache/hc/client5/http/impl/cache/ResponseCachingPolicy.java