xtract :: Functor f => (a -> f a) -> Cofree g a -> f (Cofree g a)
_extract f (a :< as) = (:< as) <$> f a
{
_extract :: Functor f => (a -> f a) -> Cofree g a -> f (Cofree g a)
_extract f (a :< as) = (:< as) <$> f a
_extract f (a :< as) = (:< as) <$> f a