docs: def list_gewesten(self, sort=1):
          '''
          List all `gewesten` in Belgium.
  
          :param integer sort: What field to sort on.
          :rtype: A :class`list` of class: `Gewest`.
          '''
          def creator():
              res = crab_gateway_request(self.client, 'ListGewesten', sort)
              tmp = {}
              for r in res.GewestItem:
                  if r.GewestId not in tmp:
                      tmp[r.GewestId] = {}
                  tmp[r.GewestId][r.TaalCodeGewestNaam] = r.GewestNaam
              return[
                  Gewest(
                      k,
                      v
                  )for k, v in tmp.items()
              ]
          if self.caches['permanent'].is_configured:
              key = 'ListGewesten#%s' % sort
              gewesten = self.caches['permanent'].get_or_create(key, creator)
          else:
              gewesten = creator()
          for g in gewesten:
              g.set_gateway(self)
          return gewesten