This property represents the "Metadata" entry of the Element.

It is an optional entry for all Dictionaries or Streams as defined as part of the PDF 1.4 specification.

A MetadataStreamElement.

For definitive details see:.

ISO 32000-1:2008 PDF 1.7; Table: 30, page 78.

Adobe Supplement to the ISO 32000, BaseVersion: 1.7, ExtensionLevel: 3; Table: 3.27, page 23.