Inheritance model update to its parent model

I need extend a model from another model.

Case:

core/models.py

class City(Master): zipcode = models.IntegerField()

Master is a abstract model.

custom/models.py

from core.models import City class City(City) newfield = models.CharField(max_length=20)

I have tried with proxy model but it is not what I need, since proxy model adds a new table. https://docs.djangoproject.com/en/2.2/topics/db/models/#proxy-models

I need is that when I migrate add the new field to City.

from Inheritance model update to its parent model