Represents the "Kids" entry of the page tree node object.

It is a required entry defined as part of the PDF 1.0 specification.

It contains an array which contains PageTreeNodeElements or PageObjectElements.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 29, page 76.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 30, page 102.