title: Initializing subset of variables in MonitoredTrainingSession
body: <p>I am using <code>MonitoredTrainingSession</code> in my training code and I want to initialize subset of weights from a checkpoint and the rest of the unassigned variables initialized to random values. I know how to do this using <code>tf.session</code> and initialize all the variables first and then read the variables from checkpoint using <code>tf.saver</code>. </p>
  
  <p>However, I don't know how to do it with <code>MonitoredTrainingSession</code>. <code>MonitoredTrainingSession</code> has bunch of advantages for me that I don't like to give up on it and switch to <code>tf.Session</code> if there's a way to make it work with <code>MonitoredTrainingSession</code>.</p>