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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.
You can't and there aren't any here. The colon is a chracter in the string to be matched, the question mark renders the preceding element optional.
lol damn never knew you could do ternany conditions inside a regex pattern