code: func (p *cadvisorStatsProvider) ImageFsDevice() (string, error) {
  	imageFsInfo, err := p.cadvisor.ImagesFsInfo()
  	if err != nil {
  		return "", err
  	}
  	return imageFsInfo.Device, nil
  }
docs: // ImageFsDevice returns name of the device where the image filesystem locates,
  // e.g. /dev/sda1.