code: def get_or_create_time_series(self, label_values):
          
          if label_values is None:
              raise ValueError
          if any(lv is None for lv in label_values):
              raise ValueError
          if len(label_values) != self._len_label_keys:
              raise ValueError
          return self._get_or_create_time_series(label_values)
docs: Get a mutable measurement for the given set of label values.
  
          :type label_values: list(:class:`LabelValue`)
          :param label_values: The measurement's label values.
  
          :rtype: :class:`GaugePointLong`, :class:`GaugePointDouble`
              :class:`opencensus.metrics.export.cumulative.CumulativePointLong`,
              or
              :class:`opencensus.metrics.export.cumulative.CumulativePointDouble`
          :return: A mutable point that represents the last value of the
              measurement.