@Nullable
    Locale selectLocale(Iterable<Locale> supportedLocales) {
        requireNonNull(supportedLocales, "supportedLocales");
        final Collection<Locale> localeCollection;
        if (supportedLocales instanceof Collection) {
            localeCollection = (Collection<Locale>) supportedLocales;
        } else {
            localeCollection = ImmutableList.copyOf(supportedLocales);
        }
        if (localeCollection.isEmpty()) {
            return null;
        }
        final List<LanguageRange> languageRanges = acceptLanguages();
        if (languageRanges == null) {
            return null;
        }
        return languageRanges
                .stream()
                .flatMap(it -> Locale.filter(ImmutableList.of(it), localeCollection).stream())
                .findFirst()
                .orElse(null);
    }
Adds the specified {@code setCookies} with {@link HttpHeaderNames#SET_COOKIE}.
core/src/main/java/com/linecorp/armeria/common/HttpHeadersBase.java