def __init__(self, backend='disk', **kwargs):
    if (backend not in self._backends):
        raise ValueError(f'Backend {backend} is not supported. Currently supported ones are {list(self._backends.keys())}')
    self.backend = backend
    self.client = self._backends[backend](**kwargs)
def __init__(self, backend='disk', **kwargs):
    if (backend not in self._backends):
        raise ValueError(f'Backend {backend} is not supported. Currently supported ones are {list(self._backends.keys())}')
    self.backend = backend
    self.client = self._backends[backend](**kwargs)