[ Tree (Cell 1:1 3:10 (NodeHeader (HeaderSection 2))) 
    [ Tree (Cell 1:4 1:8 NodePara) 
        [ Tree (Cell 1:4 1:8 (NodeToken (TokenText "sec1"))) []
        ] 
    , Tree (Cell 2:3 2:10 (NodeHeader (HeaderSection 1))) 
        [ Tree (Cell 2:5 2:10 NodePara) 
            [ Tree (Cell 2:5 2:10 (NodeToken (TokenText "sub11"))) []
            ] 
        ] 
    , Tree (Cell 3:3 3:10 (NodeHeader (HeaderSection 1))) 
        [ Tree (Cell 3:5 3:10 NodePara) 
            [ Tree (Cell 3:5 3:10 (NodeToken (TokenText "sub12"))) []
            ] 
        ] 
    ] 
]