Javadoc
Returns the native object class string for the resource object.
Native object class is the name of the Resource Object Definition (Object
Class) as it is seen by the resource itself. The name of the Resource
Object Definition may be constrained by XSD or other syntax and therefore
may be "mangled" to conform to such syntax. The native object
class value will contain unmangled name (if available).
Returns null if there is no native object class.
The exception should be never thrown unless there is some bug in the
code. The validation of model consistency should be done at the time of
schema parsing.