[lemma=tree] [tag=VBZ] [tag=CD] [□=□] □
[lemma=tree] [tag=VBZ] [tag=CD] [tag=□] □
[lemma=tree] [tag=VBZ] [tag=CD] [lemma=□] □
A tree_if contains three tree node lists : the header , the then_part , and the else_part . While BSP tree has two child node pointers at each node , ( that 's why it 's called binary tree ) TSP has three child pointers at each node .