code: func (u UUID) Variant() byte {
  	switch {
  	case (u[8] >> 7) == 0x00:
  		return VariantNCS
  	case (u[8] >> 6) == 0x02:
  		return VariantRFC4122
  	case (u[8] >> 5) == 0x06:
  		return VariantMicrosoft
  	case (u[8] >> 5) == 0x07:
  		fallthrough
  	default:
  		return VariantFuture
  	}
  }
docs: // Variant returns UUID layout variant.