code: public void registerPojoType(Class<?> type) {
  		if (type == null) {
  			throw new NullPointerException("Cannot register null type class.");
  		}
  		if (!registeredPojoTypes.contains(type)) {
  			registeredPojoTypes.add(type);
  		}
  	}
docs: Registers the given type with the serialization stack. If the type is eventually
  serialized as a POJO, then the type is registered with the POJO serializer. If the
  type ends up being serialized with Kryo, then it will be registered at Kryo to make
  sure that only tags are written.
  
  @param type The class of the type to register.