code: func (p PinSliceBySubdir) Validate(v HashAlgoValidation) error {
  	for subdir, pkgs := range p {
  		if err := ValidateSubdir(subdir); err != nil {
  			return err
  		}
  		if err := pkgs.Validate(v); err != nil {
  			return fmt.Errorf("subdir %q: %s", subdir, err)
  		}
  	}
  	return nil
  }
docs: // Validate ensures that this doesn't contain any invalid
  // subdirs, duplicate packages within the same subdir, or invalid pins.