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

It is an optional entry defined as part of the PDF 1.3 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: 220, page 433.

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.

The mapping name is used when exporting field data in column-based formats, providing a stable identifier independent of the user-visible alternate name.