Hello @nyuhnovskiy,
Since I don’t hear from you but I will be away soon, I am leaving the following suggestions and hope they will help.
If you are running it on coursera, then please follow these instructions to refresh your workspace to get back the util.py file. If you are running it on your machine, then please follow these instructions (method 2) to download all the supporting py files and put them under the same directory as the notebook file.
Good luck!
Raymond