In general, a puzzle is an "impediment" for you. When you develop some class, or a method, or a test and you can't continue - you make a stub and mark it with a `@todo` puzzle. And then you continue your course of development, on top of the stub. Later, somebody will replace the stub with a workable component and your code will continue to work as before, but with an extended functionality.

In this particular place I don't see why this is an impediment for you. What you were NOT able to develop in this branch without `RtRepo#assignees()` or `MkRepo#assignees()`? If there was something - we should see it in the branch.