isEmptyUniqSet (MkUniqSet set) = isNullUFM set {-SLOW: sizeUFM set == 0-}
-- | Invariant: the mapping function doesn't change the unique
isEmptyUniqSet (MkUniqSet set) = isNullUFM set {-SLOW: sizeUFM set == 0-}
-- | Invariant: the mapping function doesn't change the unique