is load_type necessary? The issue raised from the usage of PIDStatus.

It must be dumped as a str due to ES (PIDStatus is not JSON serializable). Then, when stored in DB it all workes because the impl of the ChoiceType is Char(1). However, if it was different it would cause problems.

The dumper should in this case be aware of loading it as the type it was before being dumped (find a way to map ChoiceType.choices)