serialization: use a post model phase to set expected attributes type

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
model: silence warnings on multiple declaration of superclasses from artifical code

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
test: update serialization tests use of attributes and super class declaration

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>