LoadError: ArgumentError: LR test is only valid for nested models

Hello! I’m trying to follow along with the “Multilevel Models in Julia” tutorial by Yichi Zhang (I can’t include a link, but it’s publicly available) using my own data. In this exercise, you implement a random intercepts model (mm1), one with only the level-2 predictor (mm2), one with only the level-1 predictor (mm3), and then one with a cross-level interaction (mm4). I was able to do all of that successfully, but when I try to call MixedModels.likelihoodratiotest(mm1,mm2,mm3,mm4) I get the foll...