code: func reversedLabelsToIPv4(labels []string) net.IP {
  	var buf strings.Builder
  
  	// If there aren't the right number of labels, it isn't an IPv4 address.
  	if len(labels) != rdnsIPv4Labels {
  		return nil
  	}
  
  	// An IPv4 address is represented as four groups of bytes separated by '.'
  	for i := len(labels) - 1; i >= 0; i-- {
  		buf.WriteString(labels[i])
  		if i != 0 {
  			buf.WriteString(".")
  		}
  	}
  	return net.ParseIP(buf.String())
  }
docs: // reversedLabelsToIPv4 reverses the provided labels (assumed to be 4 labels,
  // one per byte of the IPv6 address) and constructs an IPv4 address, returning
  // the result of calling net.ParseIP for the constructed address.