diff --git a/api/apps/sdk/session.py b/api/apps/sdk/session.py
index c5a7c4991..551f9f847 100644
--- a/api/apps/sdk/session.py
+++ b/api/apps/sdk/session.py
@@ -35,7 +35,7 @@ from api.db.services.llm_service import LLMBundle
 
 @manager.route('/chats/<chat_id>/sessions', methods=['POST'])
 @token_required
-def create(tenant_id,chat_id):
+def create(tenant_id, chat_id):
     req = request.json
     req["dialog_id"] = chat_id
     dia = DialogService.query(tenant_id=tenant_id, id=req["dialog_id"], status=StatusEnum.VALID.value)
@@ -77,7 +77,7 @@ def create_agent_session(tenant_id, agent_id):
     conv = {
         "id": get_uuid(),
         "dialog_id": cvs.id,
-        "user_id": req.get("usr_id","") if isinstance(req, dict) else "",
+        "user_id": req.get("usr_id", "") if isinstance(req, dict) else "",
         "message": [{"role": "assistant", "content": canvas.get_prologue()}],
         "source": "agent"
     }
@@ -88,11 +88,11 @@ def create_agent_session(tenant_id, agent_id):
 
 @manager.route('/chats/<chat_id>/sessions/<session_id>', methods=['PUT'])
 @token_required
-def update(tenant_id,chat_id,session_id):
+def update(tenant_id, chat_id, session_id):
     req = request.json
     req["dialog_id"] = chat_id
     conv_id = session_id
-    conv = ConversationService.query(id=conv_id,dialog_id=chat_id)
+    conv = ConversationService.query(id=conv_id, dialog_id=chat_id)
     if not conv:
         return get_error_data_result(message="Session does not exist")
     if not DialogService.query(id=chat_id, tenant_id=tenant_id, status=StatusEnum.VALID.value):
@@ -123,12 +123,12 @@ def completion(tenant_id, chat_id):
             return get_error_data_result(message="`name` can not be empty.")
         ConversationService.save(**conv)
         e, conv = ConversationService.get_by_id(conv["id"])
-        session_id=conv.id
+        session_id = conv.id
     else:
         session_id = req.get("session_id")
     if not req.get("question"):
         return get_error_data_result(message="Please input your question.")
-    conv = ConversationService.query(id=session_id,dialog_id=chat_id)
+    conv = ConversationService.query(id=session_id, dialog_id=chat_id)
     if not conv:
         return get_error_data_result(message="Session does not exist")
     conv = conv[0]
@@ -182,18 +182,18 @@ def completion(tenant_id, chat_id):
                 chunk_list.append(new_chunk)
             reference["chunks"] = chunk_list
         ans["id"] = message_id
-        ans["session_id"]=session_id
+        ans["session_id"] = session_id
 
     def stream():
         nonlocal dia, msg, req, conv
         try:
             for ans in chat(dia, msg, **req):
                 fillin_conv(ans)
-                yield "data:" + json.dumps({"code": 0,  "data": ans}, ensure_ascii=False) + "\n\n"
+                yield "data:" + json.dumps({"code": 0, "data": ans}, ensure_ascii=False) + "\n\n"
             ConversationService.update_by_id(conv.id, conv.to_dict())
         except Exception as e:
             yield "data:" + json.dumps({"code": 500, "message": str(e),
-                                        "data": {"answer": "**ERROR**: " + str(e),"reference": []}},
+                                        "data": {"answer": "**ERROR**: " + str(e), "reference": []}},
                                        ensure_ascii=False) + "\n\n"
         yield "data:" + json.dumps({"code": 0, "data": True}, ensure_ascii=False) + "\n\n"
 
@@ -235,7 +235,7 @@ def agent_completion(tenant_id, agent_id):
         conv = {
             "id": session_id,
             "dialog_id": cvs.id,
-            "user_id": req.get("user_id",""),
+            "user_id": req.get("user_id", ""),
             "message": [{"role": "assistant", "content": canvas.get_prologue()}],
             "source": "agent"
         }
@@ -251,9 +251,9 @@ def agent_completion(tenant_id, agent_id):
     question = req.get("question")
     if not question:
         return get_error_data_result("`question` is required.")
-    question={
-        "role":"user",
-        "content":question,
+    question = {
+        "role": "user",
+        "content": question,
         "id": str(uuid4())
     }
     messages.append(question)
@@ -375,7 +375,7 @@ def agent_completion(tenant_id, agent_id):
 
 @manager.route('/chats/<chat_id>/sessions', methods=['GET'])
 @token_required
-def list_session(chat_id,tenant_id):
+def list_session(chat_id, tenant_id):
     if not DialogService.query(tenant_id=tenant_id, id=chat_id, status=StatusEnum.VALID.value):
         return get_error_data_result(message=f"You don't own the assistant {chat_id}.")
     id = request.args.get("id")
@@ -387,7 +387,7 @@ def list_session(chat_id,tenant_id):
         desc = False
     else:
         desc = True
-    convs = ConversationService.get_list(chat_id,page_number,items_per_page,orderby,desc,id,name)
+    convs = ConversationService.get_list(chat_id, page_number, items_per_page, orderby, desc, id, name)
     if not convs:
         return get_result(data=[])
     for conv in convs:
@@ -429,7 +429,7 @@ def list_session(chat_id,tenant_id):
 
 @manager.route('/chats/<chat_id>/sessions', methods=["DELETE"])
 @token_required
-def delete(tenant_id,chat_id):
+def delete(tenant_id, chat_id):
     if not DialogService.query(id=chat_id, tenant_id=tenant_id, status=StatusEnum.VALID.value):
         return get_error_data_result(message="You don't own the chat")
     req = request.json
@@ -437,21 +437,22 @@ def delete(tenant_id,chat_id):
     if not req:
         ids = None
     else:
-        ids=req.get("ids")
+        ids = req.get("ids")
 
     if not ids:
         conv_list = []
         for conv in convs:
             conv_list.append(conv.id)
     else:
-        conv_list=ids
+        conv_list = ids
     for id in conv_list:
-        conv = ConversationService.query(id=id,dialog_id=chat_id)
+        conv = ConversationService.query(id=id, dialog_id=chat_id)
         if not conv:
             return get_error_data_result(message="The chat doesn't own the session")
         ConversationService.delete_by_id(id)
     return get_result()
 
+
 @manager.route('/sessions/ask', methods=['POST'])
 @token_required
 def ask_about(tenant_id):
@@ -460,17 +461,18 @@ def ask_about(tenant_id):
         return get_error_data_result("`question` is required.")
     if not req.get("dataset_ids"):
         return get_error_data_result("`dataset_ids` is required.")
-    if not isinstance(req.get("dataset_ids"),list):
+    if not isinstance(req.get("dataset_ids"), list):
         return get_error_data_result("`dataset_ids` should be a list.")
-    req["kb_ids"]=req.pop("dataset_ids")
+    req["kb_ids"] = req.pop("dataset_ids")
     for kb_id in req["kb_ids"]:
-        if not KnowledgebaseService.accessible(kb_id,tenant_id):
+        if not KnowledgebaseService.accessible(kb_id, tenant_id):
             return get_error_data_result(f"You don't own the dataset {kb_id}.")
         kbs = KnowledgebaseService.query(id=kb_id)
         kb = kbs[0]
         if kb.chunk_num == 0:
             return get_error_data_result(f"The dataset {kb_id} doesn't own parsed file")
     uid = tenant_id
+
     def stream():
         nonlocal req, uid
         try:
diff --git a/deepdoc/parser/pdf_parser.py b/deepdoc/parser/pdf_parser.py
index 9c6139469..ae663ac3c 100644
--- a/deepdoc/parser/pdf_parser.py
+++ b/deepdoc/parser/pdf_parser.py
@@ -152,7 +152,7 @@ class RAGFlowPdfParser:
             max(len(up["text"]), len(down["text"])),
             len(tks_all) - len(tks_up) - len(tks_down),
             len(tks_down) - len(tks_up),
-            tks_down[-1] == tks_up[-1],
+            tks_down[-1] == tks_up[-1] if tks_down and tks_up else False,
             max(down["in_row"], up["in_row"]),
             abs(down["in_row"] - up["in_row"]),
             len(tks_down) == 1 and rag_tokenizer.tag(tks_down[0]).find("n") >= 0,