@abc.abstractmethod<EOL><INDENT>def set_relative_start_weekday(self, weekday):<DEDENT>
pass<EOL>
Sets the relative weekday.

        :param weekday: the weekday
        :type weekday: ``cardinal``
        :raise: ``InvalidArgument`` -- ``weekday`` is invalid
        :raise: ``NoAccess`` -- ``weekday`` cannot be modified

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