@abc.abstractmethod<EOL><INDENT>def get_objectives_by_parent_genus_type(self, objective_genus_type):<DEDENT>
return<EOL>
Gets an ``ObjectiveList`` corresponding to the given objective genus ``Type`` and include any additional objective with genus types derived from the specified ``Type``.

        In plenary mode, the returned list contains all known objectives
        or an error results. Otherwise, the returned list may contain
        only those objectives that are accessible through this session

        :param objective_genus_type: an objective genus type
        :type objective_genus_type: ``osid.type.Type``
        :return: the returned ``Objective`` list
        :rtype: ``osid.learning.ObjectiveList``
        :raise: ``NullArgument`` -- ``objective_genus_type`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

        *compliance: mandatory -- This method must be implemented.*