title: How to exclude specific fields on serialization with jsonpickle?
body: <p>I'm using SQLAlchemy extension with Flask. While serializing my models <em>(which are also used for database operations)</em> using jsonpickle, I want some specific attributes to be ignored. Is there a way that allows me to set those rules?</p>
  
  <p>SQLAlchemy adds an attribute named <code>_sa_instance_state</code> to the object. In a word, I do not want this field to be in the JSON output.</p>