@abc.abstractmethod<EOL><INDENT>def get_root_qualifiers(self):<DEDENT>
return<EOL>
Gets the root qualifiers in this qualifier hierarchy.

        :return: the root qualifiers
        :rtype: ``osid.authorization.QualifierList``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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