[cem] cem by stratum

​Hello, I am looking into using CEM in a context where I need to match ​subsets of the treatment group separately based on the timing of treatment (unfortunately, the simple solution of using time as a matching component won't work in my case). After matching, I would like to combine the matched subsets to estimate a pooled treatment effect. Do the cem_weights need to be revised to account for pooling? If so, is there a reference that describes how the cem_weights are created? I understand their basic purpose - to account for differential strata sizes - but I'm not clear on the actual formula that is used to generate the weights for matched controls. Thank you, Zack