code: def get_activities_by_genus_type(self, activity_genus_type=None):
          
          if activity_genus_type is None:
              raise NullArgument()
          url_path = construct_url('activities_by_genus',
                                   bank_id=self._catalog_idstr,
                                   genus_type=activity_genus_type.get_identifier())
          return objects.ActivityList(self._get_request(url_path))
docs: Gets an ActivityList corresponding to the given activity genus
          Type which does not include activities of genus types derived
          from the specified Type.
          In plenary mode, the returned list contains all known activities
          or an error results. Otherwise, the returned list may contain
          only those activities that are accessible through this session.
          arg:    activityGenusType (osid.type.Type): an activity genus
                  type
          return: (osid.learning.ActivityList) - the returned Activity
                  list
          raise:  NullArgument - activityGenusType is null
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          compliance: mandatory - This method must be implemented.