Represents the "T" entry of the bead dictionary object.

It is defined as part of the PDF 1.0 specification.

It contains a ThreadElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 161, page 376.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 163, page 457.

The thread entry is an indirect reference to the thread dictionary that contains this bead, providing the inverse of the thread's F (first bead) entry.