@abc.abstractmethod<EOL><INDENT>def get_qualifiers(self):<DEDENT>
return<EOL>
Gets all ``Qualifiers``.

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

        :return: a list of ``Qualifiers``
        :rtype: ``osid.authorization.QualifierList``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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