code: def create_new_label_by_content_id(self, content_id, label_names, callback=None):
          
          assert isinstance(label_names, list)
          assert all(isinstance(ln, dict) and set(ln.keys()) == {"prefix", "name"} for ln in label_names)
          return self._service_post_request("rest/api/content/{id}/label".format(id=content_id),
                                           data=json.dumps(label_names), headers={"Content-Type": "application/json"},
                                           callback=callback)
docs: Adds a list of labels to the specified content.
          :param content_id (string): A string containing the id of the labels content container.
          :param label_names (list): A list of labels (strings) to apply to the content.
          :param callback: OPTIONAL: The callback to execute on the resulting data, before the method returns.
                           Default: None (no callback, raw data returned).
          :return: The JSON data returned from the content/{id}/label endpoint,
                   or the results of the callback. Will raise requests.HTTPError on bad input, potentially.