code: func (c *Manager) ListLibraryItemFiles(ctx context.Context, id string) ([]File, error) {
  	url := internal.URL(c, internal.LibraryItemFilePath).WithParameter("library_item_id", id)
  	var res []File
  	return res, c.Do(ctx, url.Request(http.MethodGet), &res)
  }
docs: // ListLibraryItemFiles returns a list of all the files for a library item.