def get_cache(option, ctx):
    if not option:
        return None

    if isinstance(option, BaseCache):
        return option
    elif isinstance(option, type) and issubclass(option, BaseCache):
        return option()

    if option is True:
        directory = path.join(ctx.directory, '.webassets-cache')
        # Auto-create the default directory
        if not path.exists(directory):
            os.makedirs(directory)
    else:
        directory = option
    return FilesystemCache(directory, ctx.cache_file_mode)
``create_volume`` returns a ``BlockDeviceVolume`` that is returned by
dataset/ETHPy150Open miracle2k/webassets/src/webassets/cache.py/get_cache--crossover with--dataset/ETHPy150Open ClusterHQ/flocker/flocker/node/agents/testtools/_blockdevice.py/IBlockDeviceAPITestsMixin.test_created_is_listed