code: def save(self):
          
          assert self.__class__ in conf.config._registry,\
              '%(class_name)s is not registered' % {
                  'class_name': self.__class__.__name__
              }
  
          ConfigModel = apps.get_model('djconfig.Config')
  
          for field_name, value in self.cleaned_data.items():
              value = utils.serialize(
                  value=value,
                  field=self.fields.get(field_name, None))
              # TODO: use update_or_create
              count = (ConfigModel.objects
                  .filter(key=field_name)
                  .update(value=value))
              if not count:
                  ConfigModel.objects.create(
                      key=field_name,
                      value=value)
  
          count = (ConfigModel.objects
              .filter(key='_updated_at')
              .update(value=str(timezone.now())))
          if not count:
              ConfigModel.objects.create(
                  key='_updated_at',
                  value=str(timezone.now()))
  
          conf.config._reload()
docs: Save the config with the cleaned data,\
          update the last modified date so\
          the config is reloaded on other process/nodes.\
          Reload the config so it can be called right away.