import VarSet ( IdSet, mkVarSet, varSetElems,
intersectVarSet, minusVarSet, extendVarSetList,
unionVarSet, unionVarSets, elemVarSet )
import VarSet ( IdSet, mkVarSet, varSetElems,
intersectVarSet, minusVarSet, extendVarSetList,
unionVarSet, unionVarSets, elemVarSet )