@abc.abstractmethod<EOL><INDENT>def get_relative_weekday_start_offset(self):<DEDENT>
return<EOL>
Gets the starting offset as the nth weekday from the relative event.

        Zero is no offset.

        :return: the offset
        :rtype: ``integer``
        :raise: ``IllegalState`` -- ``has_relative_weekday_start_offset()`` is ``false``

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