docs: def migrate_data(self, data, from_state):
          """Migrate data objects.
  
          :param data: Queryset containing all data objects that need
              to be migrated
          :param from_state: Database model state
          """
          if not self.default:
              return
  
          self.default.prepare(data, from_state)
          for instance in data:
              value = self.default.get_default_for(instance, from_state)
              if not value and not self.schema.get('required', True):
                  continue
  
              # Set default value.
              container = getattr(instance, self.schema_type, {})
              dict_dot(container, '.'.join(self.field), value)
              setattr(instance, self.schema_type, container)
              instance.save()