code: def _classnamelist(self, classname, namespace):
          
          if not classname:
              return []
  
          cn = classname.classname if isinstance(classname, CIMClassName) \
              else classname
          result = self._get_subclass_names(cn, namespace, True)
          result.append(classname)
          return result
docs: Build a list of this class and its subclasses if classname is
             a string/CIMClassName or an empty list if classname is None.
  
             Differs from _get_subclass_names in that it includes classname and
             that it returns None if there is no classname