code: func NewPCPSingletonMetric(val interface{}, name string, t MetricType, s MetricSemantics, u MetricUnit, desc ...string) (*PCPSingletonMetric, error) {
  	d, err := newpcpMetricDesc(name, t, s, u, desc...)
  	if err != nil {
  		return nil, err
  	}
  
  	sm, err := newpcpSingletonMetric(val, d)
  	if err != nil {
  		return nil, err
  	}
  
  	return &PCPSingletonMetric{sm, sync.RWMutex{}}, nil
  }
docs: // NewPCPSingletonMetric creates a new instance of PCPSingletonMetric
  // it takes 2 extra optional strings as short and long description parameters,
  // which on not being present are set to blank strings.