title: Boolean field query with sqlalchemy
body: <p>Postgres model:</p>
  
  <pre><code>class Song(db.Model):
      id3_parsed = db.Column(db.Boolean, server_default=u'false')
  </code></pre>
  
  <p>Running the following query gives the correct count:</p>
  
  <pre><code>select count(*) from song where id3_parsed is false;
  </code></pre>
  
  <p>But how do I do it with flask-sqlalchemy? This doesn't work:</p>
  
  <pre><code>songs = Song.query.filter(Song.id3_parsed == False).all()
  </code></pre>