code: func (a *API) FetchMetricClusters(extras string) (*[]MetricCluster, error) {
  	reqURL := url.URL{
  		Path: config.MetricClusterPrefix,
  	}
  
  	extra := ""
  	switch extras {
  	case "metrics":
  		extra = "_matching_metrics"
  	case "uuids":
  		extra = "_matching_uuid_metrics"
  	}
  
  	if extra != "" {
  		q := url.Values{}
  		q.Set("extra", extra)
  		reqURL.RawQuery = q.Encode()
  	}
  
  	result, err := a.Get(reqURL.String())
  	if err != nil {
  		return nil, err
  	}
  
  	var clusters []MetricCluster
  	if err := json.Unmarshal(result, &clusters); err != nil {
  		return nil, err
  	}
  
  	return &clusters, nil
  }
docs: // FetchMetricClusters retrieves all metric clusters available to API Token.