import tensorflow as tf

      if FLAGS.enbl_dst:
        logits_dst = self.helper_dst.calc_logits(self.sess_eval, images)

      # model definition - weight-sparsified model
      with tf.variable_scope(self.model_scope):
        # loss & extra evaluation metrics
        logits = self.forward_eval(images)
        loss, metrics = self.calc_loss(labels, logits, self.trainable_vars)
