docs: def set_n_of_m(self, value=None):
          """stub"""
          if value is None:
              raise NullArgument()
          if isinstance(value, bool):
              # because True / False are also int types...
              raise InvalidArgument('value must be integer')
          if value is not None and not isinstance(value, int):
              raise InvalidArgument('value must be integer')
          if self.get_n_of_m_metadata().is_read_only():
              raise NoAccess()
          if not self.my_osid_object_form._is_valid_integer(value,
                                                            self.get_n_of_m_metadata()):
              raise InvalidArgument()
          self.my_osid_object_form._my_map['nOfM'] = value