code: func CreateHealthCheck(c storagebackend.Config) (func() error, error) {
  	switch c.Type {
  	case "etcd2":
  		return nil, fmt.Errorf("%v is no longer a supported storage backend", c.Type)
  	case storagebackend.StorageTypeUnset, storagebackend.StorageTypeETCD3:
  		return newETCD3HealthCheck(c)
  	default:
  		return nil, fmt.Errorf("unknown storage type: %s", c.Type)
  	}
  }
docs: // CreateHealthCheck creates a healthcheck function based on given config.