Sort bitstreams

* Refactor get_files_from_s3 method to sort bitstreams

Author: ehanson8

dsaps/helpers.py

@@ -66,6 +66,8 @@ def get_files_from_s3(
                     continue
             item_identifier = parse_value_from_text(file_name, id_regex)
             files.setdefault(item_identifier, []).append(file_path)
+    for key, value in files.items():
+        files[key] = sorted(value, key=lambda x: x.split("_")[-1])
     return dict(sorted(files.items()))