'Driver entry point for updating a generic volume group.
Since no actual group construct is ever created in ONTAP, it is not
necessary to update any metadata on the backend. Since this is a NO-OP,
there is guaranteed to be no change in any of the volumes\' statuses.'

@utils.trace_method
def update_group(self, context, group, add_volumes=None, remove_volumes=None):

    return (None, None, None)
