Represents the "Opt" entry of the field dictionary object.

It is an optional entry defined as part of the PDF 1.4 specification.

It contains an array which contains Elements.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 220, page 432.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 226, page 527.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 222, page 434.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 228, page 529.

For choice fields Opt lists the available options as strings or two-element arrays. When two-element arrays are used the first element is the export value and the second is the display label.