### What problem does this PR solve?

Refactor Document API

### Type of change


- [x] Refactoring

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

### What problem does this PR solve?


### Type of change


- [x] Documentation Update

### What problem does this PR solve?

Refactor API for document and session.

### Type of change


- [x] Refactoring

---------

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

### What problem does this PR solve?

Refactor Chat API

### Type of change

- [x] Refactoring

---------

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

### What problem does this PR solve?

Refactor Dataset API

### Type of change

- [x] Refactoring

---------

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

### What problem does this PR solve?



### Type of change

- [x] Documentation Update