re-train using previous checkpoint

[pygabc1]

In order to re-train using previous checkpoint,
I try to change the following code in "model.py":
`self.saver = tf.train.Saver(max_to_keep=50, keep_checkpoint_every_n_hours=1)
coord = tf.train.Coordinator()
threads = tf.train.start_queue_runners(sess=sess, coord=coord)

summary_op = tf.summary.merge_all()
summary_writer = tf.summary.FileWriter(self.train_dir, sess.graph, flush_secs=30)`

to:
`# training summary
summary_op = tf.summary.merge_all()
summary_writer = tf.summary.FileWriter(self.train_dir, sess.graph, flush_secs=30)

saver = tf.train.import_meta_graph(r'./checkpoints/color/deblur.model-523000.meta')
saver.restore(sess, tf.train.latest_checkpoint(r'./checkpoints/color/'))
self.saver = saver

coord = tf.train.Coordinator()
threads = tf.train.start_queue_runners(sess=sess, coord=coord)`

However, I have an error of
ValueError: Can't load save_path when it is None
in the line of
saver.restore(sess, [tf.train.latest_checkpoint(r'./checkpoints/color/'))]