title: Python SqlAlchemy order_by DateTime?
body: <p>I'm using SqlAlchemy to store some objects with a DateTime field:</p>
  
  <pre><code>my_date = Field(DateTime())
  </code></pre>
  
  <p>I'd like to run a query to retrieve the most recent few objects (Entities with the my_date field that are the most recent).</p>
  
  <p>I've tried the following:</p>
  
  <pre><code>entities = MyEntity.query.order_by(MyEntity.time).limit(3).all()
  entities = MyEntity.query.order_by(-MyEntity.time).limit(3).all()
  </code></pre>
  
  <p>But these queries return the same objects in the same order. The SqlAlchemy documentation notes the use of the '-' to reverse the order, but I'm surely missing something here. </p>
  
  <p>Can anyone help?</p>