Got Fetch argument None has invalid type <class 'NoneType'> error

[dhirajdhakal09]

While executing session.run I got the following error, I am using Python 3, please help me asap.

This is where it is called:
File model.py
line 139: , loss, summary = self.sess.run([self.train_op, self.loss, merged],
feed_dict={self.Y: batch_images, self.X: batch_noisy, self.lr: lr[epoch],
self.is_training: True})

File "C:\Users\Acer\PycharmProjects\Test\venv\lib\site-packages\absl\app.py", line 303, in run
_run_main(main, args)
File "C:\Users\Acer\PycharmProjects\Test\venv\lib\site-packages\absl\app.py", line 251, in _run_main
sys.exit(main(argv))
File "D:/Machine Learning Data/DnCNN/DnCNN/main.py", line 57, in main
denoiser_train(model, lr=lr)
File "D:/Machine Learning Data/DnCNN/DnCNN/main.py", line 26, in denoiser_train
denoiser.train(eval_files, noisy_eval_files, batch_size=args.batch_size, ckpt_dir=args.ckpt_dir, epoch=args.epoch, lr=lr)
File "D:\Machine Learning Data\DnCNN\DnCNN\model.py", line 141, in train
self.is_training: True})
File "C:\Users\Acer\PycharmProjects\Test\venv\lib\site-packages\tensorflow\python\client\session.py", line 968, in run
run_metadata_ptr)
File "C:\Users\Acer\PycharmProjects\Test\venv\lib\site-packages\tensorflow\python\client\session.py", line 1176, in _run
self._graph, fetches, feed_dict_tensor, feed_handles=feed_handles)
File "C:\Users\Acer\PycharmProjects\Test\venv\lib\site-packages\tensorflow\python\client\session.py", line 487, in init
self._fetch_mapper = _FetchMapper.for_fetch(fetches)
File "C:\Users\Acer\PycharmProjects\Test\venv\lib\site-packages\tensorflow\python\client\session.py", line 268, in for_fetch
return _ListFetchMapper(fetch)
File "C:\Users\Acer\PycharmProjects\Test\venv\lib\site-packages\tensorflow\python\client\session.py", line 380, in init
self._mappers = [_FetchMapper.for_fetch(fetch) for fetch in fetches]
File "C:\Users\Acer\PycharmProjects\Test\venv\lib\site-packages\tensorflow\python\client\session.py", line 380, in
self._mappers = [_FetchMapper.for_fetch(fetch) for fetch in fetches]
File "C:\Users\Acer\PycharmProjects\Test\venv\lib\site-packages\tensorflow\python\client\session.py", line 265, in for_fetch
(fetch, type(fetch)))
TypeError: Fetch argument None has invalid type <class 'NoneType'>

Process finished with exit code -1

[dhirajdhakal09]

Anyone can answer my query?? Please it is very urgent///