'Unregister a handler with an event.
:type event_name: str
:param event_name: The name of the event.
:type handler: callable
:param handler: The callback to unregister.
:type unique_id: str
:param unique_id: A unique identifier identifying the callback
to unregister.  You can provide either the handler or the
unique_id, you do not have to provide both.
:param unique_id_uses_count: boolean
:param unique_id_uses_count: Specifies if the event should maintain
a count when a ``unique_id`` is registered and unregisted. The
event can only be completely unregistered once every ``register``
call using the ``unique_id`` has been matched by an ``unregister``
call. If the ``unique_id`` is specified, subsequent
``unregister`` calls must use the same value for
``unique_id_uses_count`` as the ``register`` call that first
registered the event.
:raises ValueError: If the call to ``unregister`` uses ``unique_id``
but the value for ``unique_id_uses_count`` differs from the
``unique_id_uses_count`` value declared by the very first
``register`` call for that ``unique_id``.'

def unregister(self, event_name, handler=None, unique_id=None, unique_id_uses_count=False):

    self._events.unregister(event_name, handler=handler, unique_id=unique_id, unique_id_uses_count=unique_id_uses_count)
