The rules state: "custom packages in your submission notebook will not be accepted". Could you explain what is custom package? For example, I created many *.py files (modules) and stored these files in folders (packages). Are these custom packages?
Custom packages would be any libraries/packages that are not publicly available and therefore inaccessible to all users. Scripts such as the ones you wrote are welcome(if not encouraged) as long as they utilize open source and publicly available libraries to bring your solution together.