docs: def get_content_labels(self, content_id, prefix=None, start=None, limit=None, callback=None):
          """
          Returns the list of labels on a piece of Content.
          :param content_id (string): A string containing the id of the labels content container.
          :param prefix (string): OPTIONAL: The prefixes to filter the labels with {@see Label.Prefix}.
                                  Default: None.
          :param start (int): OPTIONAL: The start point of the collection to return. Default: None (0).
          :param limit (int): OPTIONAL: The limit of the number of labels to return, this may be restricted by
                              fixed system limits. Default: 200.
          :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.
          """
          params = {}
          if prefix:
              params["prefix"] = prefix
          if start is not None:
              params["start"] = int(start)
          if limit is not None:
              params["limit"] = int(limit)
          return self._service_get_request("rest/api/content/{id}/label".format(id=content_id), params=params,
                                           callback=callback)