title: Way to disable sqlalchemy event listeners
body: <p>I use sqlalchemy 1.0.
  My project has several models, some of them have event listeners, like
  <code>event.listen(Model, 'after_update', Model._after_update)</code>.</p>
  
  <p>In case of unit-testing I need to disable all event listeners on model/session/etc.</p>
  
  <p>When particular test finished I need to enable all listeners.</p>
  
  <p>Is there any ways to achieve this?</p>