def _evaluate(self, batch_size, mode):
        if mode == "val":
            feed_dict = self.env.data_manager.do_val()
        elif mode == "test":
            feed_dict = self.env.data_manager.do_test()
        else:
            raise Exception("Unknown evaluation mode: {}".format(mode))

        sess = tf.get_default_session()
        return sess.run(self.recorded_tensors, feed_dict=feed_dict)