Test Cases (#2993)

### What problem does this PR solve?

Test Cases

### Type of change

- [x] Refactoring

Co-authored-by: liuhua <10215101452@stu.ecun.edu.cn>

api/apps/sdk/doc.py

@@ -44,6 +44,7 @@ from rag.nlp import search
 from rag.utils import rmSpace
 from rag.utils.es_conn import ELASTICSEARCH
 from rag.utils.storage_factory import STORAGE_IMPL
+import os
 
 MAXIMUM_OF_UPLOADING_FILES = 256