Doesn't create ForeignKey for inherited models

[simulyant]

I use Flask-SQLAlchemy. If models A, B inherited from model C by ForeignKey. Then migrate creates ForeignKey only for first model (A or B) and not creates ForeignKey for another model. It should create ForeignKeys for both models A and B. These are some snippets of my code:

`class Party(db.Model, UserMixin):
id = db.Column(db.Integer, primary_key=True)
...

class PartyNonAdmin(Party):
id = db.Column(db.Integer, db.ForeignKey('party.id'), primary_key=True)
...

class PartyNonAdmin2(Party):
id = db.Column(db.Integer, db.ForeignKey('party.id'), primary_key=True)
...
`
So classes PartyNonAdmin and PartyNonAdmin2 inherited from Party by ForeignKey. But when I launch db_migrate.py the ForeignKey created only for PartyNonAdmin table (the first of two tables PartyNonAdmin and PartyNonAdmin2).

I use the following db_migrate.py script:
`#!flask/bin/python
import imp
from migrate.versioning import api
from app import db
from config import SQLALCHEMY_DATABASE_URI
from config import SQLALCHEMY_MIGRATE_REPO

migration = SQLALCHEMY_MIGRATE_REPO + '/versions/%03d_migration.py' % (
api.db_version(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO) + 1)
tmp_module = imp.new_module('model')
old_model = api.create_model(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO)
exec old_model in tmp_module.dict
script = api.make_update_script_for_model(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO, tmp_module.meta,
db.metadata)
open(migration, "wt").write(script)
api.upgrade(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO)
print 'New migration saved as ' + migration
print 'Current database version: ' + str(api.db_version(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO))`