Represents the "ShadingType" entry of the shading dictionary object.

It is a required entry defined as part of the PDF 1.0 specification.

It contains an integer representing a PDF numeric object.

This item may take one of the following valid values:.

• 1
• 2
• 3
• 4
• 5
• 6
• 7

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 78, page 183.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 77, page 227.