It's not clear from the documentation how decay_lines work. I know that this is the reimplementation of the parent-child decay tree mechanism, but no new developer would know what's going on here. I think this is another reason to document these private methods and *certain* members. The problem is that I need to know what a decay_line_ is/how it works, but I don't need to know what recorded_ is. I get it, that's obvious. I think this definitely needs a CEP-level attention if PRs are still coming in without private member documentation. I'll wait for @scopatz and @gonuke to chime in.