import tensorflow as tf

        self.sess.run(tf.global_variables_initializer())

        # Tensorboard
        if summary_dir is not None:
            self.writer = tf.summary.FileWriter(summary_dir)
        tf.summary.scalar('Loss/Policy', loss_pg)
        tf.summary.scalar('Loss/Value', loss_vf)
        tf.summary.scalar('Loss/Entropy', loss_entropy)
