[Flask] Establishing foreign key back to parent class

[Tim Johnson]

FYI : Python coder 12 years in CGI and MySQL 
new to flask and SQLAlchemy.
  (have always just used MysqlDB)
  
Using SQLAlchemy Version 1.0.11 with python 2.7.6 on Ubuntu 14.04

I've followed a couple of "paint by numbers " tutorials from both th
M. Grinberg book and from the following URL
https://www.digitalocean.com/community/tutorials/how-to-structure-large-flask-applications

The second tutorial takes little different approach to setting up
data models, by implementing a base class for the date module.

The code in question can be found at the URL under the heading
"Step 2: Define The Module Data Model(s)"
Using that code generated an error for me - 
"sqlalchemy.exc.NoForeignKeysError: Can't find any foreign key
relationships between 'base' and 'auth_user'."

None of the comments at the URL reference the problem that I had,

Question 1 :
could that be because of a new version of SQLAlchemy?

I found my success by eliminating the Base class and moving the code
from the Base class in the User Class and using db.Model as the
parent class.

# My working code is as follows:
# Import the database object (db) from the main application module
# We will define this inside /app/__init__.py in the next sections.
from app import db  # SQLAlchemy instance

# Define a base model for other database tables to inherit

# class Base(db.Model):

#     __abstract_ = True
#     id = db.Column(db.Integer, primary_key=True)
#     date_created = db.Column(db.DateTime, default=db.func.current_timestamp())
#     date_modified = db.Column(db.DateTime, default=db.func.current_timestamp(),
#                               onupdate=db.func.current_timestamp())


# Define a User model
# class User(Base):
class User(db.Model):
    # The following 4 assignments are taken from the Base Class
    __abstract_ = True
    id = db.Column(db.Integer, primary_key=True)
    date_created = db.Column(db.DateTime, default=db.func.current_timestamp())
    date_modified = db.Column(db.DateTime, default=db.func.current_timestamp(),
                              onupdate=db.func.current_timestamp())

    __tablename__ = 'auth_user'

    # User Name
    name = db.Column(db.String(128), nullable=False)

    # Identification Data: email & password
    email = db.Column(db.String(128), nullable=False,
                      unique=True)
    password = db.Column(db.String(192), nullable=False)

    # Authorisation Data: role & status
    role = db.Column(db.SmallInteger, nullable=False)
    status = db.Column(db.SmallInteger, nullable=False)

    # New instance instantiation procedure
    def __init__(self, name, email, password):
        self.name = name
        self.email = email
        self.password = password

    def __repr__(self):
        return '<User %r>' % (self.name)

Question 2: What is missing from the original code using
db.Model -> Base -> User scheme?
I.E. how to establish the foreign key relationship

Thanks
-- 
Tim 
http://www.akwebsoft.com, http://www.tj49.com