{[A,[a,D,b,F]],
 [A,[C,H]],
 [B,[B,a,H]],
 [B,[b]],
 [C,[D]],
 [D,[C]],
 [D,[]],
 [E,[c,E,d]],
 [E,[b]],
 [F,[B,F]],
 [H,[C,D]],
 [H,[a]]}