docs: def _perform_unique_localized_field_checks(self, unique_checks):
          """
          Do the checks for the localized fields.
          """
          bad_fields = set()
          form_errors = []
  
          for (field_name, local_field_name) in unique_checks:
              
              lookup_kwargs = {}
              lookup_value = self.cleaned_data[field_name]
              # ModelChoiceField will return an object instance rather than
              # a raw primary key value, so convert it to a pk value before
              # using it in a lookup.
              lookup_value = getattr(lookup_value, 'pk', lookup_value)
              lookup_kwargs[str(local_field_name)] = lookup_value
  
              qs = self.instance.__class__._default_manager.filter(**lookup_kwargs)
  
              # Exclude the current object from the query if we are editing an
              # instance (as opposed to creating a new one)
              if self.instance.pk is not None:
                  qs = qs.exclude(pk=self.instance.pk)
  
              # This cute trick with extra/values is the most efficient way to
              # tell if a particular query returns any results.
              if qs.extra(select={'a': 1}).values('a').order_by():
                  self._errors[field_name] = ErrorList([self.unique_error_message([field_name])])
                  bad_fields.add(field_name)
                  
          return bad_fields, form_errors