Fix: renrank_model and pdf_parser bugs | Update: session API (#2601)

### What problem does this PR solve?

Fix: renrank_model and pdf_parser bugs | Update: session API
#2575
#2559
### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] Refactoring

---------

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

sdk/python/ragflow/modules/assistant.py

@@ -76,7 +76,7 @@ class Assistant(Base):
         raise Exception(res["retmsg"])
 
     def get_session(self, id) -> Session:
-        res = self.get("/session/get", {"id": id})
+        res = self.get("/session/get", {"id": id,"assistant_id":self.id})
         res = res.json()
         if res.get("retmsg") == "success":
             return Session(self.rag, res["data"])

sdk/python/ragflow/modules/session.py

@@ -16,9 +16,12 @@ class Session(Base):
             if "reference" in message:
                 message.pop("reference")
         res = self.post("/session/completion",
-                        {"id": self.id, "question": question, "stream": stream}, stream=True)
+                        {"session_id": self.id, "question": question, "stream": True}, stream=stream)
         for line in res.iter_lines():
             line = line.decode("utf-8")
+            if line.startswith("{"):
+                json_data = json.loads(line)
+                raise Exception(json_data["retmsg"])
             if line.startswith("data:"):
                 json_data = json.loads(line[5:])
                 if json_data["data"] != True:
@@ -69,6 +72,7 @@ class Message(Base):
         self.reference = None
         self.role = "assistant"
         self.prompt = None
+        self.id = None
         super().__init__(rag, res_dict)
 
 
@@ -76,10 +80,10 @@ class Chunk(Base):
     def __init__(self, rag, res_dict):
         self.id = None
         self.content = None
-        self.document_id = None
-        self.document_name = None
-        self.knowledgebase_id = None
-        self.image_id = None
+        self.document_id = ""
+        self.document_name = ""
+        self.knowledgebase_id = ""
+        self.image_id = ""
         self.similarity = None
         self.vector_similarity = None
         self.term_similarity = None

sdk/python/test/t_session.py

@@ -19,7 +19,7 @@ class TestSession:
         question = "What is AI"
         for ans in session.chat(question, stream=True):
             pass
-        assert ans.content!="\n**ERROR**", "Please check this error."
+        assert not ans.content.startswith("**ERROR**"), "Please check this error."
 
     def test_delete_session_with_success(self):
         rag = RAGFlow(API_KEY, HOST_ADDRESS)