How to have multiple groups in Python statsmodels linear mixed effects model?

Question

I am trying to use the Python statsmodels linear mixed effects model to fit a model that has two random intercepts, e.g. two groups. I cannot figure out how to initialize the m

Answer 1

Multiple or crossed random intercepts crossed effects can be fit using variance components, which are implemented in a different way from the one-group mixed effects.

I don't find an example, and the documentation seems to be only partially updated.

The unit tests contain an example using the MixedLM formula interface:

https://github.com/statsmodels/statsmodels/blob/master/statsmodels/regression/tests/test_lme.py#L284