SDK for session (#2354)

### What problem does this PR solve?

Includes SDK for creating, updating sessions, getting sessions, listing
sessions, and dialogues
#1102 
### Type of change

- [x] New Feature (non-breaking change which adds functionality)

---------

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

sdk/python/ragflow/ragflow.py

@@ -17,7 +17,7 @@ from typing import List
 
 import requests
 
-from .modules.chat_assistant import Assistant
+from .modules.assistant import Assistant
 from .modules.dataset import DataSet
 
 
@@ -30,8 +30,8 @@ class RAGFlow:
         self.api_url = f"{base_url}/api/{version}"
         self.authorization_header = {"Authorization": "{} {}".format("Bearer", self.user_key)}
 
-    def post(self, path, param):
-        res = requests.post(url=self.api_url + path, json=param, headers=self.authorization_header)
+    def post(self, path, param, stream=False):
+        res = requests.post(url=self.api_url + path, json=param, headers=self.authorization_header, stream=stream)
         return res
 
     def get(self, path, params=None):