 exist, as a 'Maybe'.
--
-- @
-- 'ipre' :: 'IndexedGetter' i s a     -> 'IndexPreservingGetter' s ('Maybe' (i, a))
-- 'ipre' :: 'IndexedFold' i s a       -> 'IndexPreservingGetter' s ('Maybe' (i, a))
-- 'ipre' :: 'IndexedTraversal'' i s a -> 'IndexPreservingGetter' s ('Maybe' (i, a))
-- 'ipre' :: 'IndexedLens'' i s a      -> 'IndexPreservingGetter' s ('Maybe' (i, a))
-- @
ipre :: IndexedGetting i (First (i, a)) s a -> IndexPreservingGetter s (Maybe (i, a))
ipre l = dimap (getFirst . getConst #. l (Indexed $ \i a -> Const (First (Just (i, a))))) phantom
{-# INLINE ipre #-}

------------------------------------------------------------------------------
-- Preview
------
ipre :: IndexedGetting i (First (i, a)) s a -> IndexPreservingGetter s (Maybe (i, a))
ipre l = dimap (getFirst . getConst #. l (Indexed $ \i a -> Const (First (Just (i, a))))) phantom
ipre l = dimap (getFirst . getConst #. l (Indexed $ \i a -> Const (First (Just (i, a))))) phantom