code: func WithContentTrustFromEnv() DockerCliOption {
  	return func(cli *DockerCli) error {
  		cli.contentTrust = false
  		if e := os.Getenv("DOCKER_CONTENT_TRUST"); e != "" {
  			if t, err := strconv.ParseBool(e); t || err != nil {
  				// treat any other value as true
  				cli.contentTrust = true
  			}
  		}
  		return nil
  	}
  }
docs: // WithContentTrustFromEnv enables content trust on a cli from environment variable DOCKER_CONTENT_TRUST value.