如何向与类有多对多关系的主题添加和获取标记？

Question

我想给特定班级的学生加分。其中 Subject 与 Class 有 ManyToMany 关系，而 Class 与 Student 有 ForeignKey 关系。

class Subject(models.Model):
    name = models.CharField(max_length=50)
    mark = models.IntegerField(null=True, blank=True)

    def __str__(self):
        return self.name


class Class(models.Model):
    name = models.CharField(max_length=30)
    subjects = models.ManyToManyField(Subject, blank=True)

    def __str__(self):
        return self.name

class Student(models.Model):
    name = models.CharField(max_length=100)
    class_name = models.ForeignKey(Class, on_delete=models.SET_NULL, null=True)

    def __str__(self):
        return self.name