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] (not leaf) }
      0. { 4_a_I [level 3] (not leaf) }
         0. { 4_a_I_A [level 3] } 3+
         1. { 4_a_I_B [level 3] } 3+
         2. { 4_a_I_C [level 3] }
      1. { 4_a_II [level 3] }
   1. { 4_b [unsel override] } 1+
   2. { 4_c [unsel override] }