code: func getLabelNames(datapointsLabels []datapointLabels) []string {
  	// Collect all label names used among datapointsLabels.
  	nameMap := map[string]bool{}
  	for _, kv := range datapointsLabels {
  		for k := range kv.labels {
  			nameMap[k] = true
  		}
  	}
  
  	// Return a slice of nameMap keys.
  	names := []string{}
  	for n := range nameMap {
  		names = append(names, n)
  	}
  	return names
  }
docs: // getLabelNames returns the names of all labels among datapointsLabels.