code: def get(self, permission_id, expand=[]):
          
          parent_url = self.client.get_url(self.parent_object._manager._URL_KEY, 'GET', 'single', {'id': self.parent_object.id})
          target_url = parent_url + self.client.get_url_path(
              self._URL_KEY, 'GET', 'single', {'permission_id': permission_id})
          return self._get(target_url, expand=expand)
docs: List a specific permisison for the given object.
  
          :param str permission_id: the id of the Permission to be listed.