How to apply condition in boolean field in django rest framework?

Question

I am working on a blog type website.

where students will ask question and teacher will answer it.

I put two user role Teacher and student

class User(AbstractBaseUser, PermissionsMixin):
    USER_TYPE = (
        ('None', 'None'),
        ('Student', 'Student'),
        ('Teacher', 'Teacher'),
    )
    user_type = models.CharField(choices=USER_TYPE, default='Student', max_length=50)

This is the user model where the role is defined.

Post model for submitting the question and Comment model for answering it.

In the Post model I put on field is_answered and as default put it False

class add_question(models.Model):
    created_by = models.ForeignKey(User, blank=False, on_delete=models.CASCADE)
    is_answered = models.BooleanField(default=False)

And the answer model [which is comment one] is referred to as the foreign key of the question

class submit_answer(models.Model):
    question_id = models.ForeignKey(
        add_question, blank=False, on_delete=models.CASCADE)
    created_by = models.ForeignKey(User, blank=False, on_delete=models.CASCADE)

Both question and answer model contains created_by field and ForeignKey of User and answer model contains another ForeignKey of question.

so I need when the teacher role will put a comment the is_answered Field in add_question model should turn as true. as student also can comment on his/er question so I need on condition to apply.

I am using serializer as I need API of this

So, should I modify on my views.py or serializers.py and how should I do that!

It would be great help if someone guide me how to do it?

Thanks and let me know if any other information needed.