def get_metric_values(self, group_name):
        """
        Get the faked metric values for a metric group, by its metric group
        name.

        The result includes all metric object values added earlier for that
        metric group name, using
        :meth:`~zhmcclient.FakedMetricsContextManager.add_metric_object_values`
        i.e. the metric values for all resources and all points in time that
        were added.

        Parameters:

          group_name (:term:`string`): Name of the metric group.

        Returns:

          iterable of :class:`~zhmclient.FakedMetricObjectValues`: The metric
            values for that metric group, in the order they had been added.

        Raises:

          ValueError: Metric values for this group name do not exist.
        """
        if group_name not in self._metric_values:
            raise ValueError("Metric values for this group name do not "
                             "exist: {}".format(group_name))
        return self._metric_values[group_name]
Get the faked metric values for a metric group, by its metric group
        name.

        The result includes all metric object values added earlier for that
        metric group name, using
        :meth:`~zhmcclient.FakedMetricsContextManager.add_metric_object_values`
        i.e. the metric values for all resources and all points in time that
        were added.

        Parameters:

          group_name (:term:`string`): Name of the metric group.

        Returns:

          iterable of :class:`~zhmclient.FakedMetricObjectValues`: The metric
            values for that metric group, in the order they had been added.

        Raises:

          ValueError: Metric values for this group name do not exist.