+ collectInBlock :: BlockElement -> [BlockElement]
+ collectInBlock hd@(Heading _ _)
+ = [hd]
+ collectInBlock (Div _ xs)
+ = concatMap collectInBlock $ catMaybes (map castToBlock xs)
+ collectInBlock (BlockCmd (BlockCommand _ _ xs))
+ = concatMap collectInBlock xs
+ collectInBlock _
+ = []