@Nullable
    @Override
    public List<String> cachedHeaders() {
        final String val = getNormalized("cachedHeaders");
        if (val == null) {
            return null;
        }
        return CSV_SPLITTER.splitToList(val);
    }
Implementation of {@link FlagsProvider} which provides values from JVM options to {@link Flags}.
core/src/main/java/com/linecorp/armeria/common/SystemPropertyFlagsProvider.java