0. { item_0 } 0+
1. { item_1 } 0+
2. { item_2 } 0+
3. { item_3 } 0+
4. { item_4 (not leaf) }
   0. { 4_a [level 2] } 1+
   1. { 4_b [unsel override] } 1+
   2. { 4_c [unsel override] (not leaf) }
      0. { 4_c_I [unsel override 2] } 2+
      1. { 4_c_II [unsel override 2] } 2+
      2. { 4_c_III [sel override 2] }