@abc.abstractmethod<EOL><INDENT>def get_superseded_event_position(self):<DEDENT>
return<EOL>
Gets the position in the denormalized recurring series of the event to replace.

        Positive numbers count from the start and negative numbers count
        from the end. Zero is invalid.

        :return: the position of the event to replace
        :rtype: ``integer``
        :raise: ``IllegalState`` -- ``supersedes_by_position()`` is ``false``

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