Get hierarchy
[]
[1]
[2,1]
[3,1]
[4,2,1]
[]
Get is in hierarchy
1
1
0
Get children
[1]
[2,3]
[4]
[]
[]
[]
Get all descendants
[1,2,3,4]
[2,3,4]
[4]
[]
[]
[]
Get descendants at first level
[1]
[2,3]
[4]
[]
[]
[]