new_contents: # -*- coding: utf-8 -*-
  # Generated by Django 1.11.1 on 2017-05-09 09:05
  from __future__ import unicode_literals
  from django.contrib.postgres.operations import HStoreExtension
  import django.contrib.postgres.fields.hstore
  from django.db import migrations
  
  
  class Migration(migrations.Migration):
  
      dependencies = [
          ('topics', '0050_merge_20170508_0249'),
      ]
  
      operations = [
          HStoreExtension(),
          migrations.AddField(
              model_name='lesson',
              name='heading_tree',
              field=django.contrib.postgres.fields.hstore.HStoreField(null=True),
          ),
      ]
  
subject: Add migration file