@abc.abstractmethod<EOL><INDENT>def get_packages_by_parent_genus_type(self, package_genus_type):<DEDENT>
return<EOL>
Gets a ``PackageList`` corresponding to the given package genus ``Type`` and include any additional package
        with genus types derived from the specified ``Type``.

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

        :param package_genus_type: a package genus type
        :type package_genus_type: ``osid.type.Type``
        :return: the returned ``Package`` list
        :rtype: ``osid.installation.PackageList``
        :raise: ``NullArgument`` -- ``package_genus_type`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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