Fix bugs in agent api and update api document (#3996)

### What problem does this PR solve?

Fix bugs in agent api and update api document

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)

---------

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

docs/references/python_api_reference.md

@@ -14,6 +14,13 @@ Dataset Management
 :::
 
 ---
+### Install the RAGFlow SDK
+
+To install the RAGFlow SDK, run the following command in your terminal:
+
+```bash
+pip install ragflow-sdk
+```
 
 ## Create dataset
 
@@ -1401,7 +1408,7 @@ while True:
 ---
 
 ## Create session with agent
-
+*If there are parameters in the `begin` component, the session cannot be created in this way.*
 ```python
 Agent.create_session(id,rag) -> Session
 ```
@@ -1428,7 +1435,7 @@ session = create_session(AGENT_ID,rag_object)
 
 ---
 
-## Converse with agent
+## Converse with agent without `begin` component
 
 ```python
 Session.ask(question: str, stream: bool = False) -> Optional[Message, iter[Message]]