This property represents the "Kids" entry of the number tree
node dictionary object.
It is defined as part of the PDF 1.0 specification.
An Array containing child NumberTreeNodeElements which may be
intermediate or leaf nodes.
This entry is always null in leaf nodes. In intermediate nodes
it must always be non-null.
In the root node either this entry or the EntryNums entry should be non-null. But not
For definitive details see:.
The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 37,