private boolean addFast(Iterable<? extends Map.Entry<? extends IN_NAME, ?>> entries) {
        if (!(entries instanceof StringMultimap)) {
            return false;
        }

        @SuppressWarnings("unchecked")
        final StringMultimap<IN_NAME, NAME> multimap = (StringMultimap<IN_NAME, NAME>) entries;
        Entry e = multimap.firstGroupHead.after;
        while (e != multimap.firstGroupHead) {
            final NAME key = e.key;
            final String value = e.value;
            assert key != null;
            assert value != null;
            addAndNotify(e.hash, index(e.hash), key, value, true);
            e = e.after;
        }

        return true;
    }
Invoked when all values are cleared.
core/src/main/java/com/linecorp/armeria/common/StringMultimap.java