title: How does SQLAlchemy create_engine import Engine class?
body: <p>I am relatively new to python and am experimenting with SQLAlchemy. I noticed that, to create an engine, I have to use the <code>create_engine()</code> function, imported via <code>from sqlalchemy import create_engine</code>.</p>
  
  <p>Now, the <code>create_engine</code> function returns an instance of the <code>sqlalchemy.engine.base.Engine</code> class. However I never imported this class, I only imported the <code>create_engine</code> module. So, how does Python know about the <code>sqlalchemy.engine.base.Engine</code> class?</p>