MessagePack msgpack = new MessagePack();
Unconverter packer = new Unconverter(msgpack);
if (v == null) {
packer.writeNil();
} else {
packer.writeMapBegin(v.size());
for (Map.Entry<K, V> e : ((Map<K, V>) v).entrySet()) {
packer.write(e.getKey());
packer.write(e.getValue());
}
packer.writeMapEnd();