无法向django ManyToManyfield添加数据

from django.db import models

class Student(models.Model):
    name = models.CharField(max_length=100)
    courses = models.ManyToManyField('Course')

class Course(models.Model):
    name = models.CharField(max_length=100)

# 创建学生和课程对象
student = Student.objects.create(name='Alice')
course = Course.objects.create(name='Math')

# 添加多对多关系
student.courses.add(course)

class StudentCourse(models.Model):
    student = models.ForeignKey(Student, on_delete=models.CASCADE)
    course = models.ForeignKey(Course, on_delete=models.CASCADE)

# 创建学生和课程对象
student = Student.objects.create(name='Alice')
course = Course.objects.create(name='Math')

# 通过中间模型添加关系
StudentCourse.objects.create(student=student, course=course)