code: def get_qs(self):
          
          qs = url_params_from_lookup_dict(self.rel.limit_choices_to)
          if not qs:
              qs = {}
  
          if self.extra_query_kwargs:
              qs.update(self.extra_query_kwargs)
          return qs
docs: Returns a mapping that will be used to generate
          the query string for the api url. Any values
          in the the `limit_choices_to` specified on the
          foreign key field and any arguments specified on
          self.extra_query_kwargs are converted to a format
          that can be used in a query string and returned as
          a dictionary.