Represents the "Language" entry of the optional content usage dictionary object.

It is an optional entry defined as part of the PDF 1.0 specification.

It contains an OptionalContentUsageLanguageElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 102, page 232.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 100, page 285.

The Language sub-dictionary associates the group with a language. It contains a Lang entry with an RFC 3066 language tag and an optional Preferred entry. Viewers that perform automatic language-based state setting use this information.