def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def queue_when_in_transaction(call):
    if transaction_states[call.using]:
        transaction_states[call.using].push((call, (), {}))
    else:
        return call()