code: func IsCleanPointerError(err error) bool {
  	if e, ok := err.(interface {
  		CleanPointerError() bool
  	}); ok {
  		return e.CleanPointerError()
  	}
  	if parent := parentOf(err); parent != nil {
  		return IsCleanPointerError(parent)
  	}
  	return false
  }
docs: // IsCleanPointerError indicates an error while cleaning a file.