Update the celery task comment and name (#720)

backend/app/task/tasks/tasks.py

@@ -1,12 +1,21 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
-from anyio import sleep
+from time import sleep
+
+from anyio import sleep as asleep
 
 from backend.app.task.celery import celery_app
 
 
+@celery_app.task(name='task_demo')
+def task_demo() -> str:
+    """示例任务，模拟耗时操作"""
+    sleep(20)
+    return 'test async'
+
+
 @celery_app.task(name='task_demo_async')
 async def task_demo_async() -> str:
     """异步示例任务，模拟耗时操作"""
-    await sleep(20)
+    await asleep(20)
     return 'test async'