code: func (d *DockerValidator) Validate(spec SysSpec) (error, error) {
  	if spec.RuntimeSpec.DockerSpec == nil {
  		// If DockerSpec is not specified, assume current runtime is not
  		// docker, skip the docker configuration validation.
  		return nil, nil
  	}
  
  	c, err := client.NewClient(dockerEndpoint, "", nil, nil)
  	if err != nil {
  		return nil, errors.Wrap(err, "failed to create docker client")
  	}
  	info, err := c.Info(context.Background())
  	if err != nil {
  		return nil, errors.Wrap(err, "failed to get docker info")
  	}
  	return d.validateDockerInfo(spec.RuntimeSpec.DockerSpec, info)
  }
docs: // Validate is part of the system.Validator interface.
  // TODO(random-liu): Add more validating items.