code: func (p *Plugin) Register(registryPath string, collector prometheus.Collector) error {
  	p.Lock()
  	defer p.Unlock()
  
  	reg, found := p.regs[registryPath]
  	if !found {
  		p.Log.WithField("path", registryPath).Error(ErrRegistryNotFound)
  		return ErrRegistryNotFound
  	}
  	return reg.Register(collector)
  }
docs: // Register registers prometheus metric to a specified registry. In order to add metrics
  // to default registry use prometheus.DefaultRegistry const.