rack_download.RdRetrieves the raw file path(s) for a stored session identified by id from
the given backend. This is a low-level generic; most callers should use
rack_load() instead.
rack_download(id, backend, ...)A character vector of local file paths to the downloaded content.
rack_load() for the high-level wrapper that parses the result,
rack_upload() for the complementary upload generic.