title: How to subclass the default `db.Model` to use as a custom `Base` with SQLAlchemy
body: <p>I have a flask application spread across modules with blueprints.
  Each module/blueprint has its own models.py file where models are defined.</p>
  
  <p>With my desktop applications, using SQLAlchemy API directly, I would subclass <code>object</code> to define a <code>Base</code> class with some columns (ex: <code>id</code>, <code>date_created</code> ..), which then would serve as my declarative base (ex: <code>Base = declarative_base(cls=Base)</code>).</p>
  
  <ul>
  <li>How can I subclass <code>flask-SQLALchemy</code>'s <code>db.Model</code> so that I can use it as a Base with default columns which I want all tables to have?</li>
  </ul>