code: func (os *OpenStack) DiskIsAttached(instanceID, volumeID string) (bool, error) {
  	if instanceID == "" {
  		klog.Warningf("calling DiskIsAttached with empty instanceid: %s %s", instanceID, volumeID)
  	}
  	volume, err := os.getVolume(volumeID)
  	if err != nil {
  		return false, err
  	}
  
  	return instanceID == volume.AttachedServerID, nil
  }
docs: // DiskIsAttached queries if a volume is attached to a compute instance