code: func init() {
  	graphdriver.Register("windowsfilter", InitFilter)
  	// DOCKER_WINDOWSFILTER_NOREEXEC allows for inline processing which makes
  	// debugging issues in the re-exec codepath significantly easier.
  	if os.Getenv("DOCKER_WINDOWSFILTER_NOREEXEC") != "" {
  		logrus.Warnf("WindowsGraphDriver is set to not re-exec. This is intended for debugging purposes only.")
  		noreexec = true
  	} else {
  		reexec.Register("docker-windows-write-layer", writeLayerReexec)
  	}
  }
docs: // init registers the windows graph drivers to the register.