src/main/java/de/javakaffee/kryoserializers/guava/ImmutableMultimapSerializer.java
private static Serializer<?> getSerializer(Kryo kryo, Class<?> type) {
        Registration registration = kryo.getClassResolver().getRegistration(type);
        return registration != null ? registration.getSerializer() : null;
    }
private static Serializer<?> getSerializer(Kryo kryo, Class<?> type) {
        Registration registration = kryo.getClassResolver().getRegistration(type);
        return registration != null ? registration.getSerializer() : null;
    }
/* kryo.getSerializer (invoking kryo.getRegistration) throws an exception if registration is required,
therefore we're getting a potentially existing serializer on another way.