title: Unbind object from session
body: <p>Is it possible to unbind an object from an SQLAlchemy session?</p>
  
  <p>I used to <code>deepcopy</code> it, but as this <a href="https://stackoverflow.com/q/11155106/145013">seems not to be possible</a> when using association proxies I'm searching for another solution to remove the object from a session to add it to another one.</p>