@abc.abstractmethod<EOL><INDENT>def get_uncertainty_units(self):<DEDENT>
return<EOL>
Gets the units of the uncertainty.

        :return: units of the uncertainty
        :rtype: ``osid.calendaring.DateTimeResolution``
        :raise: ``IllegalState`` -- ``defines_uncertainty()`` is ``false``

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