-- | /O(n+m)/. Is this a submap?
-- Defined as (@'isSubmapOf' = 'isSubmapOfBy' (==)@).
isSubmapOf :: Eq a => IntMap a -> IntMap a -> Bool
IntMap m1 `isSubmapOf` IntMap m2 = m1 `W.isSubmapOf` m2
isSubmapOf :: Eq a => IntMap a -> IntMap a -> Bool
IntMap m1 `isSubmapOf` IntMap m2 = m1 `W.isSubmapOf` m2
IntMap m1 `isSubmapOf` IntMap m2 = m1 `W.isSubmapOf` m2