title: Unexpected working of new attribute of Session class in Flask
body: <p>According to the <a href="http://flask.pocoo.org/docs/0.12/api/#flask.session.new" rel="nofollow noreferrer">Flask</a> documentation, <code>new</code> attribute returns <code>True</code> if the session is new. otherwise <code>False</code>, but in my case, it always returns <code>False</code> no matter what. Here is the code:</p>
  
  <pre><code>@app.route('/set-session/')
  def testing_session():
      session['user_id'] = 'jon'
      print(session.new)    # always returns True . Why ?
      print(session.modified)
      return 'playing with session'
  </code></pre>