docs: def get_postadres_by_subadres(self, subadres):
          '''
          Get the `postadres` for a :class:`Subadres`.
  
          :param subadres: The :class:`Subadres` for which the \
              `postadres` is wanted. OR A subadres id.
          :rtype: A :class:`str`.
          '''
          try:
              id = subadres.id
          except AttributeError:
              id = subadres
          def creator():
              res = crab_gateway_request(
                  self.client, 'GetPostadresBySubadresId', id
              )
              if res == None:
                   raise GatewayResourceNotFoundException()
              return res.Postadres
          if self.caches['short'].is_configured:
              key = 'GetPostadresBySubadresId#%s' % (id)
              postadres = self.caches['short'].get_or_create(key, creator)
          else:
              postadres = creator()
          return postadres