code: def get_next_grade(self):
          
          try:
              next_object = next(self)
          except StopIteration:
              raise IllegalState('no more elements available in this list')
          except Exception:  # Need to specify exceptions here!
              raise OperationFailed()
          else:
              return next_object
docs: Gets the next ``Grade`` in this list.
  
          return: (osid.grading.Grade) - the next ``Grade`` in this list.
                  The ``has_next()`` method should be used to test that a
                  next ``Grade`` is available before calling this method.
          raise:  IllegalState - no more elements available in this list
          raise:  OperationFailed - unable to complete request
          *compliance: mandatory -- This method must be implemented.*