head
    :: Monad m
    => EC2 m (ResumableSource m a)
    -> EC2 m (Maybe a)
head src = do
    s <- src
    lift $ s $$+- CL.head
head
    :: Monad m
    => EC2 m (ResumableSource m a)
    -> EC2 m (Maybe a)
head src = do
    s <- src
    lift $ s $$+- CL.head
head src = do
    s <- src
    lift $ s $$+- CL.head