code: func (p *Plugin) Init() error {
  	p.regs = map[string]*registry{}
  
  	// add default registry
  	p.regs[DefaultRegistry] = &registry{
  		Gatherer:   prometheus.DefaultGatherer,
  		Registerer: prometheus.DefaultRegisterer,
  	}
  
  	return nil
  }
docs: // Init initializes the internal structures