Agents will try to enter. The pub checks if it is possible

def enter(self, pub_id, *nodes):
        '''Agents will try to enter. The pub checks if it is possible'''
        try:
            pub = self['pubs'][pub_id]
        except KeyError:
            raise ValueError('Pub {} is not available'.format(pub_id))
        if not pub['open'] or (pub['capacity'] < (len(nodes) + pub['occupancy'])):
            return False
        pub['occupancy'] += len(nodes)
        for node in nodes:
            node['pub'] = pub_id
        return True