prop_strict :: BagTest a bag => bag a -> bag a -> Bool
prop_strict bag xs =
   strict xs === xs
   &&
   strictWith id xs === xs
prop_strict :: BagTest a bag => bag a -> bag a -> Bool
prop_strict bag xs =
   strict xs === xs
   &&
   strictWith id xs === xs
prop_strict bag xs =
   strict xs === xs
   &&
   strictWith id xs === xs