code: func DeviceChangeString(specs []types.BaseVirtualDeviceConfigSpec) string {
  	var strs []string
  	for _, v := range specs {
  		spec := v.GetVirtualDeviceConfigSpec()
  		strs = append(strs, fmt.Sprintf("(%s: %T at key %d)", string(spec.Operation), spec.Device, spec.Device.GetVirtualDevice().Key))
  	}
  	return strings.Join(strs, ",")
  }
docs: // DeviceChangeString pretty-prints a slice of VirtualDeviceConfigSpec.