code: public SerializerRegistry registerAbstract(Class<?> abstractType, TypeSerializerFactory factory) {
      return registerAbstract(abstractType, calculateTypeId(abstractType), factory);
    }
docs: Registers the given class as an abstract serializer for the given abstract type.
  
  @param abstractType The abstract type for which to register the serializer.
  @param factory The serializer factory.
  @return The serializer registry.