class TimeLayer:

    def __init__(self):
        self.layer = {}

    def add_event(self, event):
        if 'ses' not in event:
            return
        hostname = event['hostname']
        ses = event['ses']
        timestamp = event['timestamp']
        event_id = event['event_id']
        self.layer.setdefault(hostname, {ses: {timestamp: [event_id]}})
        self.layer[hostname].setdefault(ses, {timestamp: [event_id]})
        self.layer[hostname][ses].setdefault(timestamp, [event_id])
        if hostname in self.layer.keys():
            if ses in self.layer[hostname].keys():
                if timestamp in self.layer[hostname][ses]:
                    if event_id not in self.layer[hostname][ses][timestamp]:
                        self.layer[hostname][ses][timestamp].append(event_id)