'Restores the model from the given checkpoint path into the session.
Args:
checkpoint_path: File pathname of the checkpoint.
sess:            Session in which to restore the model.
Returns:
global_step of the model.'

def Restore(self, checkpoint_path, sess):

    self.saver.restore(sess, checkpoint_path)
    return tf.train.global_step(sess, self.global_step)
