def dataset_backend(self):
        """
        Get the storage driver the acceptance testing nodes will use.

        :return: A ``BackendDescription`` matching the name of the backend
            chosen by the command-line options.
        """
        configuration = self.dataset_backend_configuration()
        # Avoid requiring repetition of the backend name when it is the same as
        # the name of the configuration section.  But allow it so that there
        # can be "great-openstack-provider" and "better-openstack-provider"
        # sections side-by-side that both use "openstack" backend but configure
        # it slightly differently.
        dataset_backend_name = configuration.get(
            "backend", self["dataset-backend"]
        )
        try:
            return backend_loader.get(dataset_backend_name)
        except __HOLE__:
            raise UsageError(
                "Unknown dataset backend: {}".format(
                    dataset_backend_name
                )
            )
dataset/ETHPy150Open ClusterHQ/flocker/admin/acceptance.py/CommonOptions.dataset_backend