It seems that I have fulfilled requirements of protocol EveryUserDocument in class GetListItem, however the code doesn’t compile returning me error: Type ‘GetListItem’ does not conform to protocol ‘EveryUserDocument’. Can somebody explain why and how to do a workaround?

I have protocols:

I’m studying the Collection protocol and decided to implement my own collection, but I didn’t stop there and wanted to implement the index(after:) method so that it works the other way around