def events_mark_seen(self, event):
last_seen = event if isinstance(event, int) else event.id<EOL>self.client.post('<STR_LIT>'.format(Event.api_endpoint), model=Event(self.client, last_seen))<EOL>
Marks event as the last event we have seen.  If event is an int, it is treated
as an event_id, otherwise it should be an event object whose id will be used.