private void setIfAbsentSlow(Iterable<? extends Map.Entry<? extends IN_NAME, String>> entries,
                                 Set<NAME> existingNames) {

        for (Map.Entry<? extends IN_NAME, String> e : entries) {
            final NAME key = normalizeName(e.getKey());
            if (!existingNames.contains(key)) {
                add(key, e.getValue());
            }
        }
    }
Invoked when all values are cleared.
core/src/main/java/com/linecorp/armeria/common/StringMultimap.java