title: Python, SqlAlchemy: Many to many relationship, find those without
body: <p>Say I have two types of objects, <code>Movies</code> and <code>Tags</code>, related by the <a href="http://www.sqlalchemy.org/docs/orm/mapper_config.html#" rel="nofollow">ORM</a> in a <a href="http://www.sqlalchemy.org/docs/orm/relationships.html#many-to-many" rel="nofollow">many to many relationship</a> with an association table indicated by the <code>secondary</code> argument to <code>relationship()</code>, and I want to be able to find, say, all the <code>Movies</code> without <code>Tags</code>? What kind of query would I run to achieve that effect?</p>