The tutorial states the command [create-collection](https://github.com/oxheadalpha/nft-tutorial/tree/master/packages/tznft#originate-nft-collection-contract) and I cannot find the definition of this contract. There is the [tutorial](https://github.com/oxheadalpha/nft-tutorial/blob/master/packages/fa2-contracts/README.md) on how to create a custom modular contract but how do I specify to use this custom version?