@abc.abstractmethod<EOL><INDENT>def get_families_by_genus_type(self, family_genus_type):<DEDENT>
return<EOL>
Gets a ``FamilyList`` corresponding to the given family genus ``Type`` which does not include families of genus types derived from the specified ``Type``.

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

        :param family_genus_type: a family genus type
        :type family_genus_type: ``osid.type.Type``
        :return: the returned ``Family list``
        :rtype: ``osid.relationship.FamilyList``
        :raise: ``NullArgument`` -- ``family_genus_type`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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