[ Tree (Cell 1:1 3:11 (NodeHeader (HeaderSection 1))) 
    [ Tree (Cell 1:3 1:7 NodePara) 
        [ Tree (Cell 1:3 1:7 (NodeToken (TokenText "sec1"))) []
        ] 
    , Tree (Cell 2:3 2:11 (NodeHeader (HeaderSection 2))) 
        [ Tree (Cell 2:6 2:11 NodePara) 
            [ Tree (Cell 2:6 2:11 (NodeToken (TokenText "sub11"))) []
            ] 
        ] 
    , Tree (Cell 3:3 3:11 (NodeHeader (HeaderSection 2))) 
        [ Tree (Cell 3:6 3:11 NodePara) 
            [ Tree (Cell 3:6 3:11 (NodeToken (TokenText "sub12"))) []
            ] 
        ] 
    ] 
]