code: func ContainerMetric(appID string, instance int32, cpu float64, mem, disk uint64) metric_sender.ContainerMetricChainer {
  	if metricSender == nil {
  		return nil
  	}
  	return metricSender.ContainerMetric(appID, instance, cpu, mem, disk)
  }
docs: // ContainerMetric creates a container metric that can be manipulated via
  // cascading calls and then sent.