def get_client(self):
        if self.client is None:
            raise AttributeError('`self.client` is `None`')
        return self.client
Copy a value from an old flag to a new one, warning the user.
dataset/ETHPy150Open flashingpumpkin/django-socialregistration/socialregistration/mixins.py/ClientMixin.get_client--crossover with--dataset/ETHPy150Open GoogleCloudPlatform/PerfKitBenchmarker/perfkitbenchmarker/disk.py/WarnAndCopyFlag