It does work in 6.1. You have to override the _constraints list as well as the function, even if you don't want to change it. Only then will it show up in cls.__dict__.get('_constraints', []).
It does work in 6.1. You have to override the _constraints list as well as the function, even if you don't want to change it. _.get(' _constraints' , []).
Only then will it show up in cls.__dict_