code: func (ms *MetricSender) Value(name string, value float64, unit string) ValueChainer {
  	chainer := valueChainer{}
  	chainer.emitter = ms.eventEmitter
  	chainer.envelope = &events.Envelope{
  		Origin:    proto.String(ms.eventEmitter.Origin()),
  		EventType: events.Envelope_ValueMetric.Enum(),
  		ValueMetric: &events.ValueMetric{
  			Name:  proto.String(name),
  			Value: proto.Float64(value),
  			Unit:  proto.String(unit),
  		},
  	}
  	return chainer
  }
docs: // Value creates a value metric that can be manipulated via cascading calls
  // and then sent.