@Override
    public final void forEachValue(IN_NAME name, Consumer<String> action) {
        requireNonNull(name, "name");
        requireNonNull(action, "action");
        for (final Iterator<String> i = valueIterator(name); i.hasNext();) {
            action.accept(i.next());
        }
    }
Validates the given user-specified {@code value}.
core/src/main/java/com/linecorp/armeria/common/StringMultimap.java