This class represents the type 4 function dictionary. This is definitively detailed in:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; page 97.

This class is always an indirect object because it is also a StreamElement and these are always indirect objects.

System.Object
    WebSupergoo.ABCpdf13.Elements.Element
       WebSupergoo.ABCpdf13.Elements.FunctionElement
          WebSupergoo.ABCpdf13.Elements.Type4FunctionElement