Python Django not working change in sqllite database, what is the error?

Question

Django

Greetings!
As part of a tutorial project, I'm experimenting with migrations in django. The task is to change the data in an existing table in one of the columns. sqllite database. According to the documentation https://docs.djangoproject.com/en/2.0/topics/migra... I create an empty migration. I write my own function in it. I'm running the migration. The migration is running successfully. The data in the database does not change. I tried several times - the result is zero. If I delete something, add it to the models, then the migrations are performed without problems. But there is no way to change the data. Below is the migration code....

# Generated by Django 2.0.2 on 2018-03-13 19:18

from django.db import migrations

def combine(apps, schema_editor):
    Comments = apps.get_model('article', 'Comments')
    for comment in Comments.objects.all():
        comment.comments_test = 'hello-world'
        comment.save

class Migration(migrations.Migration):

    dependencies = [
        ('article', '0021_auto_20180312_2238'),
    ]

    operations = [
        migrations.RunPython(combine),
    ]