Represents the "Folders" entry of the collection dictionary object.

It is defined as part of the PDF 1.7 Extension Level 3 specification.

It contains a FolderElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 155, page 371.

Adobe Supplement to the ISO 32000, BaseVersion: 1.7, ExtensionLevel: 3; Table: 8.6, page 29.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 153, page 447.

The folder entry references the root of the folder hierarchy, separate from the flat file list, allowing the portfolio to present files organised into logical groups.