-// CollectionFileReader returns a Reader that reads file content from
-// a collection. The filename must be given relative to the root of
-// the collection, without a leading "./".
-func (kc *KeepClient) CollectionFileReader(collection map[string]interface{}, filename string) (Reader, error) {
+// CollectionFileReader returns a Reader that reads content from a single file
+// in the collection. The filename must be relative to the root of the
+// collection. A leading prefix of "/" or "./" in the filename is ignored.
+func (kc *KeepClient) CollectionFileReader(collection map[string]interface{}, filename string) (arvados.File, error) {