Register a compound statistic with this sensor which
        yields multiple measurable quantities (like a histogram)

        Arguments:
            stat (AbstractCompoundStat): The stat to register
            config (MetricConfig): The configuration for this stat.
                If None then the stat will use the default configuration
                for this sensor.

def add_compound(self, compound_stat, config=None):
        """
        Register a compound statistic with this sensor which
        yields multiple measurable quantities (like a histogram)

        Arguments:
            stat (AbstractCompoundStat): The stat to register
            config (MetricConfig): The configuration for this stat.
                If None then the stat will use the default configuration
                for this sensor.
        """
        if not compound_stat:
            raise ValueError('compound stat must be non-empty')
        self._stats.append(compound_stat)
        for named_measurable in compound_stat.stats():
            metric = KafkaMetric(named_measurable.name, named_measurable.stat,
                                 config or self._config)
            self._registry.register_metric(metric)
            self._metrics.append(metric)