Represents the "I" entry of the list field object.

It is defined as part of the PDF 1.4 specification.

It contains an array which contains integers, representing PDF numeric objects.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 231, page 445.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 234, page 539.

The I array lists the zero-based indices of all currently selected options. For single-selection lists it contains at most one element; for multi-selection lists it may contain multiple indices in ascending order.