Represents the "E" entry of the structure element dictionary object.

It is an optional entry defined as part of the PDF 1.5 specification.

It contains a string representing a PDF string object.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 323, page 559.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 355, page 722.

The E entry holds an expansion of an abbreviation or acronym used as the element content. Screen readers use this to speak the full form rather than attempting to pronounce the abbreviation.