@abc.abstractmethod<EOL><INDENT>def get_ids_by_authority(self, authority):<DEDENT>
return<EOL>
Gets ``Ids`` by the given authority.

        :param authority: an authority
        :type authority: ``string``
        :return: a list of ``Ids``
        :rtype: ``osid.id.IdList``
        :raise: ``NullArgument`` -- ``authority`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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