Root object of a type definition hierarchy.
 The TypeHier object is a toplevel object in a class volume, and act as
 the anscestor to the type definition hierarchy.
 It should be named 'Type', and there kan only be one $TypeDef object in a
 ClassVolume.

 Below the $TypeHier object, all the types in the volume are defined with
 $Type or $TypeDef objects.

See also

• $Type
• $TypeDef