Represents the "Type" entry of the page tree node object.
It is a required entry defined as part of the PDF 1.0
It contains a string representing a PDF name object.
This item must always be provided and must always take the value
For definitive details see:.
The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 29,
The ISO PDF
Specification, ISO 32000-2:2017 PDF 2.0; Table: 30, page 102.