Recall @ K

Thanks for this library. I notice that recall @ K doesn't seem to be available as one of the evaluation metrics in the latest version. Is it possible to include this?

A version of the recall @ k seems to be included here in an old commit https://github.com/thisisjl/implicit/blob/master/implicit/evaluation.pyx

Thanks!

Start by comparing the requested recall@K metric with the older implementation in implicit/evaluation.pyx, then locate the current LightFM evaluation entry point. Done means recall@K is available among the library's evaluation metrics and produces the expected recall-at-K result.

Written by the indexing model from the issue text.