def has_key(self, key, version=None):
        return self.get(key, version=version) is not None
Someone has joined a room, either a remote user or a local user
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/core/cache/backends/base.py/BaseCache.has_key--crossover with--dataset/ETHPy150Open matrix-org/synapse/contrib/experiments/test_messaging.py/HomeServer._on_join