这里为啥会报错

    def update(self,id,**kwargs):
if(id not in self.students):
return print("学生学号不存在")
if(id in self.students):
self.students[id]=kwargs
            res=self.students[id]
print(res)
print("id是{}的学生信息已被删除，新的学生信息是班级是：{}班 姓名是：{} 年龄是:{} 性别是:{}".format(id,res["class_"],res["name"],res["age"],res["sex"]))
return print("更新成功")

if __name__ == '__main__':
    users={
1:{"name":"蔡明","age":18,"class_":"A","sex":"girl"},
        2:{"name":"冯剑","age":19,"class_":"c","sex":"boy"},
        3:{"name":"余湘情","age":18,"class_":"A","sex":"girl"},
        4:{"name":"石嘉","age":17,"class_":"B","sex":"boy"},
        5:{"name":"陈玉","age":18,"class_":"A","sex":"girl"},
    }
    stus=Students_info(users)
    stus.get()
    stus.update(id=3,kwargs={"name":"石嘉1","age":17,"class_":"B","sex":"boy"})
print("--------")

结果是：

/Users/fengjian/PycharmProjects/pythonProject1/venv/bin/python /Users/fengjian/PycharmProjects/pythonProject1/test_day3_/students_info.py

Traceback (most recent call last):

  File "/Users/fengjian/PycharmProjects/pythonProject1/test_day3_/students_info.py", line 88, in <module>

    stus.update(id=3,kwargs={"name":"石嘉1","age":17,"class_":"B","sex":"boy"})

  File "/Users/fengjian/PycharmProjects/pythonProject1/test_day3_/students_info.py", line 76, in update

    print("id是{}的学生信息已被删除，新的学生信息是班级是：{}班 姓名是：{} 年龄是:{} 性别是:{}".format(id,res["class_"],res["name"],res["age"],res["sex"]))

KeyError: 'class_'

{'kwargs': {'name': '石嘉1', 'age': 17, 'class_': 'B', 'sex': 'boy'}}

Process finished with exit code 1