strict digraph {
        node [shape=box]
        graph [newrank=true ranksep=0.3 nodesep=0.5]

        func1 [style=rounded]
        func1 -> do_thing1 -> do_thing2 -> do_thing3 -> do_thing4 -> end

        func2 [style=rounded]
        func2 -> do_foo -> do_bar
        do_thing1:e -> func2:w [constraint=false]

        do_bar -> func3 [style=invis]
        func3 [style=rounded]
        func3 -> do_hoge -> do_fuga
        do_thing2:e -> func3:w [constraint=false]
}