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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
It is not advisible at all to use any mutating lists in Kotlin as long as it's easy to prevent! Don't use mutableList, don't use foreach, if all you need is a map...
But also, the many Pairs created here are a little bit too much for the task, don't you think?
Your solution creates a lot of unnecessary memory objects on the run...