def is_effective_by_event(self):
raise errors.Unimplemented()<EOL>
Tests if the effectiveness of the enabler is governed by an ``Event`` such that the start and end dates of the event govern the effectiveness.

        The event may also be a ``RecurringEvent`` in which case the
        enabler is effective for start and end dates of each event in
        the series If an event exists, it is bounded by the effective
        dates of this enabler. If ``is_effective_by_event()`` is
        ``true,`` ``is_effective_by_schedule()`` and
        ``is_effective_by_cyclic_event()`` must be ``false``.

        return: (boolean) - ``true`` if the enabler is governed by an
                event, ``false`` otherwise
        *compliance: mandatory -- This method must be implemented.*