lift (Nothing, _) = Nothing
lift (Just b, bs) = Just (b, bs)
--- | 'insertBlock' should not be used to *replace* an existing block
+-- | 'insertBlock' should not be used to /replace/ an existing block
-- but only to insert a new one
insertBlock :: Block m l -> BlockEnv (Block m l) -> BlockEnv (Block m l)
insertBlock b bs =