Fix some issues in API and test (#3001)

### What problem does this PR solve?

Fix some issues in API and test

### Type of change

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

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

sdk/python/ragflow/modules/chat.py

@@ -9,7 +9,7 @@ class Chat(Base):
         self.id = ""
         self.name = "assistant"
         self.avatar = "path/to/avatar"
-        self.datasets = ["kb1"]
+        self.dataset_ids = ["kb1"]
         self.llm = Chat.LLM(rag, {})
         self.prompt = Chat.Prompt(rag, {})
         super().__init__(rag, res_dict)