FILE: main.kt
    public final fun main(x: R|kotlin/collections/MutableCollection<kotlin/collections/Set<kotlin/String>>|): R|kotlin/Unit| {
        lval y: R|ft<@FlexibleNullability kotlin/collections/MutableList<ft<kotlin/String, kotlin/String?>!>, kotlin/collections/List<ft<kotlin/String, kotlin/String?>!>?>!| = Q|ContainerUtil|.R|/ContainerUtil.flatten|<R|ft<kotlin/String, kotlin/String?>!|>(R|<local>/x|)
        R|<local>/y|.R|SubstitutionOverride<kotlin/collections/MutableList.get: R|ft<kotlin/String, kotlin/String?>!|>|(Int(0)).R|kotlin/String.length|
    }
