code: func (ms *MetricSender) ContainerMetric(appID string, instance int32, cpu float64, mem, disk uint64) ContainerMetricChainer {
  	chainer := containerMetricChainer{}
  	chainer.emitter = ms.eventEmitter
  	chainer.envelope = &events.Envelope{
  		Origin:    proto.String(ms.eventEmitter.Origin()),
  		EventType: events.Envelope_ContainerMetric.Enum(),
  		ContainerMetric: &events.ContainerMetric{
  			ApplicationId: proto.String(appID),
  			InstanceIndex: proto.Int32(instance),
  			CpuPercentage: proto.Float64(cpu),
  			MemoryBytes:   proto.Uint64(mem),
  			DiskBytes:     proto.Uint64(disk),
  		},
  	}
  	return chainer
  }
docs: // ContainerMetric creates a container metric that can be manipulated via
  // cascading calls and then sent.